USOO8336443B2
(12) United States Patent
Abe et al.
(54) HYDRAULIC WORKING MACHINE
(10) Patent No.:
US 8,336,443 B2
(45) Date of Patent:
*Dec. 25, 2012
(56)
References Cited
(75) Inventors: Toshihiro Abe, Osaka (JP); Yusuke
U.S. PATENT DOCUMENTS
Kajita, Ushiku (JP); Kazunori
5,174,189 A
12, 1992 Kamimura
Nakamura, Tsuchiura (JP): Kouji
Ishikawa, Niihari-gun (JP); Hideo
5,442,912 A ck
7,562,615 B2
8, 1995 Hirata et al.
7/2009 Abe et al. ........................ 91f436
Karasawa, Tsuchiura (JP)
FOREIGN PATENT DOCUMENTS
EP
O 262 098
GB
JP
JP
06-144794
5, 1994
(*) Notice:
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
JP
WO
O7-305379
WO94/13959
11, 1995
6, 1994
U.S.C. 154(b) by 99 days.
* cited by examiner
This patent is Subject to a terminal dis-
Primary Examiner — F. Daniel Lopez
Ca10.
(21) Appl. No.: 12/428,203
(22) Filed:
Apr. 22, 2009
(65)
lug. 13,
O
chamber 11a and rod chamber 12b of the boom cylinder 11,
Related U.S. Application Data
(62) Division of application No. 10/542,201, filed as
application No. PCT/JP2004/000168 on Jan. 14, 2004,
now Pat. No. 7,562,615.
(30)
8, 1984
2, 1990
(74) Attorney, Agent, or Firm — Crowell & Moring LLP
(57)
ABSTRACT
A hydraulic circuit for a hydraulic working machine is com
posed of a main pump 21, a boom cylinder 11 arranged for
extension or contraction by pressure oil from the main pump
21, a directional control valve 22 for controlling flows of
pressure oil to be fed from the main pump 21 to a bottom
Prior Publication Data
US 2009/O199552 A1
Aug. 13, 2009
O
2134 187 A
2-18496
3, 1988
(73) Assignee: Hitachi Construction Machinery Co.,
Ltd., Tokyo (JP)
a control unit 23 for performing a change-over control of the
directional control valve 22, a pilot pump 24, ajack-up selec
tor valve 25 for controlling a flow of pressure oil delivered
from the pilot pump 24, a flow control valve 26 connected on
an upstream side of the directional control valve 22 to a
meter-in port of the directional control valve 22 such that the
flow control valve 26 can be changed over by the jack-up
selector valve 25, and a center bypass selector valve 27 con
Foreign Application Priority Data
Jan. 14, 2003
(JP) ................................. 2003-OO5808
May 21, 2003
(JP) ................................. 2003-143632
nected on a downstream side of the directional control valve
(51) Int. Cl.
FI5B II/024
(2006.01)
(52) U.S. Cl. ............................... 91/436; 91/445; 91/446
22 to a center bypass port of the directional control valve 22
such that the center bypass selector valve 27 can be changed
over by the jack-up selector valve 25. The hydraulic circuit
performs a change-over of the jack-up selector valve 25 in
(58) Field of Classification Search .................... 60/468;
accordance with a bottom pressure on the boom cylinder 11.
91/436, 445, 446
See application file for complete search history.
4 Claims, 14 Drawing Sheets
08
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U.S. Patent
Dec. 25, 2012
Sheet 1 of 14
FIG. 1
US 8,336,443 B2
U.S. Patent
Dec. 25, 2012
Sheet 2 of 14
FIG 2
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U.S. Patent
Dec. 25, 2012
Sheet 3 of 14
FIG 3
US 8,336,443 B2
U.S. Patent
Sheet 4 of 14
Dec. 25, 2012
US 8,336,443 B2
FIG 4
40
24 G() 21
---------------
CNI CO og
11b
39
U.S. Patent
Dec. 25, 2012
Sheet 5 of 14
US 8,336,443 B2
FIG. 5
-41
25
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38
l
39
-28
- - - INSTRUCTION Pi
73 INSTRUCTION Pi
T-an-Tri
N
BM LOWERINGP
- - - - -- -
BM/B PRESSURE
- - 64
51
U.S. Patent
Dec. 25, 2012
Sheet 6 of 14
US 8,336,443 B2
FIG. 6
3a
40
|NS
RUCTION Pi
-
X
INSTRUCTION Pi
U.S. Patent
Dec. 25, 2012
Sheet 7 of 14
FIG 7
28
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X
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104b.
O4C
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US 8,336,443 B2
U.S. Patent
Dec. 25, 2012
Sheet 8 of 14
FIG. 8
US 8,336,443 B2
U.S. Patent
Dec. 25, 2012
Sheet 9 of 14
US 8,336,443 B2
FIG. 9
OUTPUT SIDE
INPUT SIDE
SHUTLE WALWE GROUP 3O
RIGHT
TRACK FORWARD
O
-
O
Af
Afa
RIGHT
O
TRACK REARWARD
Ar
3O8
LEFT
TRACK FORWARD !
Bf
LEFT
302
4.
OPERATION
Bf
TRACK REARWARD
Br
Br
S
313
BUCKET CROWING
CC
/
titlá
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PUMP CONTROL
SIGNALXp1
CC
3O3
BUCKET DUMPING
Cd
Cd
BOOM RASING
Du
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3O4
JACK UP
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ARM CROWDING
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tuft."
SIGNALXf
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ARM DUMPNG
Ed
Ed
312
SWING-TO-RIGHT
Fr
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306
SWING-TO-LEFT
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RESERVE
307
F.
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RESERVE 2
BOOM LOWERING
Dd
DC
sareas
or
rim
as
umams
a
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U.S. Patent
US 8,336,443 B2
11b
53
U.S. Patent
Dec. 25, 2012
Sheet 11 of 14
US 8,336,443 B2
FIG 11
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PO
BM LOWERING P.
BM/B PRESSURE
64
U.S. Patent
Dec. 25, 2012
Sheet 12 of 14
US 8,336,443 B2
FIG. 12
23a
- - - -- ---- - - -
-
.S. 2
|NSTRUCTION Pi
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g2 91
INSTRUCTION Pi
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U.S. Patent
Dec. 25, 2012
Sheet 13 of 14
US 8,336,443 B2
-- - - - - -- -- - -- - - -- -- - - - -
28
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108
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U.S. Patent
Dec. 25, 2012
Sheet 14 of 14
US 8,336,443 B2
INPUT SIDE
OUTPUT SIDE
SHUTTLE WALVE GROUP 3O
RIGHT
TRACK FORWARD
- ---- - C-- - -
Af
Af
301
FRIGHT
TRACK REARWARD
A
Ar
TRACK
TRACK FORWARD
Bf
LEFT
&
SIGNA Xt
302 N
317
Br
BUCKET CROWDING
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B. CONTROL
- tuNZ NPUMP
SIGNAL Xp1
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BUCKET DUMPING
CC
Bf
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3O3 O
Cd
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ARM CROWDIN
ARM DUMPINGEd
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US 8,336,443 B2
1.
HYDRAULIC WORKING MACHINE
CROSS-REFERENCE TO RELATED
APPLICATIONS
2
main pump is not fed to the rod chamber of the boom cylinder
and the horse power consumption of the pump conversely
becomes greater than the regeneration of only the return oil
from the bottom chamber in the rod chamber of the boom
cylinder without feeding pressure oil from the main pump to
the
rod chamber, because of the construction that the pressure
This Application is a divisional of application Ser. No.
oil from the main pump is normally fed to the rod chamber of
10/542,201, filed Jan. 31, 2006; which is based upon 35
U.S.C. 371 Application No. PCT/JP2004/000168 filed Jan. the boom cylinder upon lowering the boom. Moreover, the
14, 2004, further claiming priority to Japanese Patent Appli pressure oil delivered from the main pump is fed to the rod
cation No.JP 2003-005808 filed Jan. 14, 2003 and JP 2003 10 chamber of the boom cylinder when another working element
is driven while allowing the boom to fall. This leads to a
143632 filed May 21, 2003.
relative decrease in the amount of pressure oil to be fed to the
actuator for driving another working element, thereby incon
TECHNICAL FIELD
Veniently developing poor energy efficiency. It is to be noted
This invention relates to a hydraulic working machine Such 15 that a jack-up is performed, for example, upon escaping from
as a hydraulic excavator in which working elements such as a a Swamp or upon travelling while Supporting a boom by the
boom, arm and bucket are driven by double-acting hydraulic body when moving down on and along a steep slope.
The present invention has been completed to resolve such
cylinders, and specifically to a hydraulic circuit construction
for feeding pressure oil to bottom chambers and rod chambers defects of the conventional technologies, and its object is to
provide a hydraulic working machine that makes it possible to
of the hydraulic cylinders.
achieve a reduction in the horsepower consumption of a main
pump and an improvement in energy efficiency upon per
BACKGROUND ART
forming a simple lowering operation of a working element
Conventionally-known, hydraulic working machines and also to produce a large pressing force Such as a jack-up
include those provided with a travelling state detection means 25 force for a body.
To achieve the above-described object, the present inven
for detecting their travelling state and a selector valve for
changing over a pilot line, through which a pilot signal for tion is characterized, in a first aspect thereof, in that in a
lowering a boom (in a direction to cause contraction of a hydraulic working machine provided with a double-acting
hydraulic cylinder for the boom) is transmitted, to a cut-off hydraulic cylinder arranged for extension or contraction by
position or a communicating position on the basis of a signal 30 pressure oil, which is delivered from a main pump, to drive a
from the travelling state detection means such that, when a working element, a directional control valve for controlling a
combined operation of a travelling operation and a boom flow of pressure oil to be fed from the main pump to the
lowering operation is performed by changing over the selec hydraulic cylinder, and a control unit for performing a
tor valve to the pilot-line-communicating position upon change-over control of the directional control valve, the
detection of a travelling state by the travelling state detection 35 hydraulic working machine is provided with a jack-up selec
means, pressure oil is fed from a main pump to a rod chamber tor valve for being changed over in flow-line when a feed
of the hydraulic cylinder for the boom to permit a jack-up of pressure to the hydraulic cylinder has reached a predeter
mined pressure, and a flow-line changing means for changing
a body by the boom (see, for example, Patent Document 1
a flow-line for pressure oil, which is to be fed from the main
JP-A-06-002344, FIG. 1).
The conventionally-known, hydraulic working machines 40 pump to a meter-in port of the directional control valve, from
also include those of the type that upon lowering a boom, an open side to a closed side in response to a change-over
return oil from a bottom chamber of a boom cylinder is control of the selector valve, wherein, when the holding pres
regenerated in a rod chamber of the boom cylinder to permit Sure on the hydraulic cylinder is equal to or higher than the
avoiding fluctuations in boom operating speed, which would predetermined pressure upon lowering the working element,
otherwise take place as a result of changes or the like in an 45 the jack-up selector valve is changed over to a first selected
external force applied to the boom cylinder, while making it position to change over the flow-line changing means to the
possible to reduce the horse power consumption of a main closed side such that pressure oil delivered from the main
pump (see, for example, Patent Document 2—JP-A-05 pump is not fed to a non-holding pressure feeding side of the
hydraulic cylinder, and when the holding pressure on the
302604, FIG. 1).
50 hydraulic cylinder is lower than the predetermined pressure
DISCLOSURE OF THE INVENTION
upon lowering the working element, the jack-up selector
valve is changed over to a second selected position to change
Of the above-described conventional technologies, the over the flow-line changing means to the open side Such that
technology disclosed in Patent Document 1 involves an pressure oil delivered from the main pump is fed to a holding
inconvenience in that, when a pressing force is applied to the 55 pressure side of the hydraulic cylinder via the directional
boom in the course of a simple boom-lowering operation, the control valve.
rod chamber of the boom cylinder is brought into a vacuum
To achieve the above-descried object, the present invention
state to form a cavity and hence to have a tendency to develop is also constructed, in a second aspect thereof. Such that in a
an operational delay in the operation of the boom, because the hydraulic working machine provided with a main pump, a
pressure oil from the main pump is fed to the rod chamber of 60 working element, a double-acting hydraulic cylinder
the boom cylinder only when the combined operation of the arranged for extension or contraction by pressure oil, which is
travelling operation and the boom-lowering operation is per delivered from a main pump, to drive the working element, a
formed.
directional control valve for controlling flows of pressure oil
The technology disclosed in Patent Document 2, on the to be fed from the main pump to a bottom chamber and rod
other hand, is accompanied by an inconvenience in that, in a 65 chamber of the hydraulic cylinder, and a control unit for
simple boom-lowering operation which does not require any performing a change-over control of the directional control
pressing force to jack up a body, the pressure oil from the valve, the hydraulic working machine is provided with a
US 8,336,443 B2
4
3
jack-up selector valve for being changed over when a bottom pumps, to drive the working element, a third directional con
pressure on the hydraulic cylinder has reached a predeter trol valve for controlling flows of pressure oil to be fed from
mined pressure, and a flow-line changing means for changing the first main pump to a bottom chamber and rod chamber of
a flow-line for pressure oil, which is to be fed from the main the hydraulic cylinder, a fourth directional control valve for
pump to a meter-in port of the directional control valve, from 5 controlling flows of pressure oil to be fed from the second
an open side to a closed side in response to a change-over main pump to the bottom chamber and rod chamber of the
control of the jack-up selector valve, wherein, when the bot hydraulic cylinder, a first control unit for performing change
tom pressure on the hydraulic cylinder is equal to or higher over controls of the first and second directional control
than the predetermined pressure upon lowering the working valves, and a second control unit for performing change-over
element, the jack-up selector valve is changed over to a first 10 controls of the third and fourth directional control valves, the
selected position to change over the flow-line changing hydraulic working machine is provided with a jack-up selec
means to the closed side such that pressure oil delivered from tor valve for being changed over when a bottom pressure on
the main pump is not fed to the rod chamber of the hydraulic the hydraulic cylinder has reached a predetermined pressure,
cylinder, and when the bottom pressure on the hydraulic and a flow-line changing means for changing a flow-line for
cylinder is lower than the predetermined pressure upon low 15 pressure oil, which is to be fed from the first main pump to a
ering the working element, the jack-up selector valve is meter-in port of the third directional control valve, from an
changed over to a second selected position to change over the open side to a closed side in response to a change-over control
flow-line changing means to the open side Such that pressure of the jack-up selector valve, wherein, when the bottom pres
oil delivered from the main pump is fed to the rod chamber of Sure on the hydraulic cylinder is equal to or higher than the
predetermined pressure upon lowering the working element,
the hydraulic cylinder via the directional control valve.
For example, a hydraulic cylinder for a boom, the hydraulic the jack-up selector valve is changed over to a first selected
cylinder is being arranged on a hydraulic excavator, has a high position to change over the flow-line changing means to the
pressure on the side of its bottom chamber under the weight of closed side such that pressure oil delivered from the first and
the boom, an arm or the like as a working element in a state second main pumps is not fed to the rod chamber of the
that no external force is acting. When a pressing force is 25 hydraulic cylinder, and when the bottom pressure on the
applied to the working element, on the other hand, a pulling hydraulic cylinder is lower than the predetermined pressure
force is applied to the hydraulic cylinder for the boom so that upon lowering the working element, the jack-up selector
the hydraulic cylinder has a low pressure on the side of its valve is changed over to a second selected position to change
bottom chamber. Therefore, by monitoring changes in the over the flow-line changing means to the open side Such that
bottom pressure and, when the bottom pressure on the 30 pressure oil delivered from the first and second main pumps is
hydraulic cylinder for driving the working element is equal to fed to the rod chamber of the hydraulic cylinder via the third
or higher than the predetermined pressure upon lowering the and fourth directional control valves.
working element, changing over the jack-up selector valve to
In this construction, it is also possible to exhibit similar
the first selected position to change over the flow-line chang advantageous effects as the above-described second means
ing means to the closed side Such that pressure oil delivered 35 for resolving the defects, that is, to achieve a reduction in the
from the main pump is not fed to the rod chamber of the horsepower consumption of the pump and an improvement in
hydraulic cylinder, the horsepower consumption of the pump the energy efficiency of the hydraulic working machine upon
can be reduced upon performing a simple lowering operation performing a simple lowering operation of the working ele
of the working element that does not require any pressing ment, and further, to produce a large pressing force at the
force for jacking up the body and, when a working element is 40 working element. In addition, owing to the arrangement of the
operated in combination with allowing another working ele travelling hydraulic circuit, it is also possible to jack up the
ment to fall, pressure oil to be fed to an actuator from the main body by performing a combined operation of a traveling
pump to drive the first-mentioned working element can be operation and a working-element-lowering operation.
relatively increased. Accordingly, the energy efficiency of the
To achieve the above-described object, the present inven
hydraulic working machine can be improved. When the bot 45 tion is constructed, in a fourth aspect thereof. Such that in the
tom pressure on the hydraulic cylinder is lower than the hydraulic working machine of the above-described first or
predetermined pressure upon lowering the working element second construction, the hydraulic working machine is fur
and the jack-up selector valve is changed over to the second ther provided with a regeneration circuit for regenerating a
selected position to change over the flow-line changing portion of meter-out oil, which is discharged from the bottom
means to the open side such that the pressure oil delivered 50 chamber of the hydraulic cylinder, into meter-in oil to be fed
from the main pump is fed to the rod chamber of the hydraulic to the rod chamber of the hydraulic cylinder.
When a regeneration circuit is arranged as described
cylinder via the directional control valve, on the other hand, a
large pressing force can be produced at the working element, above, regenerated oil is fed from the bottom chamber to the
thereby making it possible to jack up the body.
rod chamber of the hydraulic cylinder even when a pressing
To achieve the above-described object, the present inven 55 force is applied to the working element in the course of a
tion is also constructed, in a third aspect thereof. Such that in simple lowering operation of the working element. It is, there
a hydraulic working machine provided with a first and second fore, possible to prevent the rod chamber of the hydraulic
main pumps, a first track unit for being driven by pressure oil cylinder from being brought into a vacuum state to form a
delivered from the first main pump, a second track unit for cavity, and hence, to continue a smooth operation of the
being driven by pressure oil delivered from the second main 60 working element.
pump, a first directional control valve for controlling a flow of
To achieve the above-described object, the present inven
pressure oil to be fed from the first main pump to the first track tion is also constructed Such that in the hydraulic working
unit, a second directional control valve for controlling a flow machine of any one of the above-described constructions, the
of pressure oil to be fed from the second main pump to the hydraulic working machine is provided with a hydraulically
second track unit, a working element, a double-acting 65 piloted selector valve as the jack-up selector valve.
When a hydraulically-piloted selector valve is arranged as
hydraulic cylinder arranged for extension or contraction by
pressure oil, which is delivered from the first and second main the jack-up selector valve as described above, it is only nec
US 8,336,443 B2
5
6
forming
a
simple
lowering
operation
of the working element
essary to connect a signal port of the jack-up selector valve
and the bottom chamber of the hydraulic cylinder with each that does not require any pressing force for jacking up the
other via a line, so that the construction is simple. It is, body and, when a working element is operated in combina
accordingly, possible to realize at low costa hydraulic work tion with allowing another working element to fall, pressure
ing machine which can achieve a reduction in the horsepower oil to be fed to an actuator from the variable displacement
consumption of the pump and an improvement in energy hydraulic pump to drive the first-mentioned working element
efficiency upon performing a simple lowering operation of can be relatively increased. Accordingly, the energy effi
ciency of the hydraulic working machine can be improved.
the working element and can also jack up the body.
To achieve the above-described object, the present inven When the holding pressure on the actuator is lower than the
tion is also constructed, in a fifth aspect thereof. Such that in 10 predetermined pressure upon lowering the working element
a hydraulic working machine provided with a variable dis and the jack-up selector valve is changed over to the second
placement hydraulic pump as a main pump, a Swash angle selected position to change over the flow-line changing
control means for controlling a displacement of the variable means to the open side such that the pressure oil delivered
displacement hydraulic pump, at least one working element, from the variable displacement hydraulic pump is fed to the
at least one actuator arranged for extension or contraction by 15 actuator via the directional control valve, on the other hand, a
pressure oil, which is delivered from the variable displace large pressing force can be produced at the working element,
ment hydraulic pump, to drive the working element, a direc thereby making it possible to jack up the body. In addition,
tional control valve for controlling a flow of pressure oil to be when the holding pressure on the actuator for driving the
fed from the variable displacement hydraulic pump to the working element is equal to or higher than the predetermined
hydraulic cylinder, a pilot control unit for controlling a stroke pressure upon lowering the working element, the displace
of the directional control valve, and a Swash angle instruction ment of the variable displacement hydraulic pump is decreas
means for outputting a Swash angle control signal to the ingly controlled, and when the holding pressure on the actua
Swash angle control means in response to a signal from the tor is lower than the predetermined pressure upon lowering
pilot control unit, the hydraulic working machine is provided the working element, the displacement of the variable dis
with a jack-up selector valve for being changed over when a 25 placement hydraulic pump is increasingly controlled by the
holding pressure on the actuator has reached a predetermined Swash angle instruction means. This makes it possible to
pressure, and a flow-line changing means for changing a reduce the horse power consumption of the pump upon per
flow-line for pressure oil, which is to be fed from the variable forming a simple lowering operation of the working element
displacement hydraulic pump to a meter-in port of the direc and hence to reduce the fuel consumption of the hydraulic
tional control valve, from an open side to a closed side in 30 working machine, and further, to promptly feed to the actua
response to a change-over control of the jack-up selector torpressure oil as much as needed upon performing a pressing
valve, wherein, when the holding pressure on the actuator is operation of the working element. It is, therefore, possible to
equal to or higher than the predetermined pressure upon low Smoothly effect a Switchover from a simple lowering opera
ering the working element, the jack-up selector valve is tion of the working element to a pressing operation of the
changed over to a first selected position to change over the 35 working element.
flow-line changing means to the closed side Such that pressure
To achieve the above-described object, the present inven
oil to be fed from the variable displacement hydraulic pump tion is also constructed, in a sixth aspect thereof. Such that in
to the actuator is cut off and the displacement of the variable a hydraulic working machine provided with a first and second
displacement hydraulic pump is decreasingly controlled, and variable displacement hydraulic pumps as main pumps, a first
when the holding pressure on the actuator is lower than the 40 and second Swash angle control means for independently
predetermined pressure upon lowering the working element, controlling displacements of the first and second variable
the jack-up selector valve is changed over to a second selected displacement hydraulic pumps, respectively, a first track unit
position to change over the flow-line changing means to the for being driven by pressure oil delivered from the first vari
open side such that pressure oil delivered from the variable able displacement hydraulic pump, a second track unit for
displacement hydraulic pump is fed to the actuator via the 45 being driven by pressure oil delivered from the second vari
directional control valve and the displacement of the variable able displacement hydraulic pump, a first directional control
displacement hydraulic pump is increasingly controlled by valve for controlling a flow of pressure oil to be fed from the
first variable displacement hydraulic pump to the first track
the Swash angle instruction means.
For example, a hydraulic cylinder for a boom, said hydrau unit, a second directional control valve for controlling a flow
lic cylinder is being arranged on a hydraulic excavator, has a 50 of pressure oil to be fed from the second variable displace
high pressure on the side of its bottom chamber under the ment hydraulic pump to the second track unit, at least one
weight of the boom, an arm or the like as a working element working element, at least one actuator arranged for extension
in a state that no external force is acting. When a pressing or contraction by pressure oil, which is delivered from the first
force is applied to the working element, on the other hand, a and second variable displacement hydraulic pumps, to drive
pulling force is applied to the hydraulic cylinder for the boom 55 the working element, a third directional control valve for
so that the hydraulic cylinder has a low pressure on the side of controlling a flow of pressure oil to be fed from the first
its bottom chamber. Therefore, by monitoring changes in the variable displacement hydraulic pump to the actuator, a
holding pressure on an actuator Such as the bottom pressure fourth directional control valve for controlling a flow of pres
on the hydraulic cylinder for the boom and, when the holding sure oil to be fed from the second variable displacement
pressure on the hydraulic cylinder for driving the working 60 hydraulic pump to the actuator, a pilot control unit for per
element is equal to or higher than the predetermined pressure forming change-over controls of the first and second direc
upon lowering the working element, changing over the jack tional control valves, and a Swash angle instruction means for
up selector valve to the first selected position to change over outputting a Swash angle control signal to the Swash angle
the flow-line changing means to the closed side Such that control means in response to a signal from the pilot control
pressure oil delivered from the variable displacement hydrau 65 unit, the hydraulic working machine is provided with a jack
lic pump as a main pump is not fed to the actuator, the horse up selector valve for being changed over when a holding
power consumption of the pump can be reduced upon per pressure on the actuator has reached a predetermined pres
US 8,336,443 B2
7
8
Sure, and a flow-line changing means for changing a flow-line from the main pump returns to a pressure oil reservoir through
for pressure oil, which is to be fed from the first variable the center bypassport of the directional control valve and the
displacement hydraulic pump to a meter-in port of the third center bypass selector valve so that the feeding of the pressure
directional control valve, from an open side to a closed side in oil to the rod chamber of the hydraulic cylinder is stopped.
response to a change-over control of the jack-up selector When the jack-up selector valve has been changed over to the
valve, wherein, when the holding pressure on the actuator is second selected position, in other words, a pressing force is
equal to or higher than the predetermined pressure upon low applied to the working element, the flow control valve is
ering the working element, the jack-up selector valve is changed over to the open position and the center bypass
changed over to a first selected position to change over the selector valve is changed over to the closed position. As a
flow-line changing means to the closed side Such that pressure 10 result, the pressure oil delivered from the main pump is fed to
oil to be fed from the first and second variable displacement the rod chamber of the hydraulic cylinder through the flow
hydraulic pumps to the actuator is cut off and the displace control valve and the meter-in port of the directional control
ments of the first and second variable displacement hydraulic valve. It is, therefore, possible achieve a reduction in the horse
pumps are decreasingly controlled, and when the holding power consumption of the pump and an improvement in the
pressure on the actuator is lower than the predetermined 15 energy efficiency of the hydraulic working machine upon
pressure upon lowering the working element, the jack-up performing a simple lowering operation of the working ele
selector valve is changed over to a second selected position to ment. In addition, it is also possible to produce a large press
change over the flow-line changing means to the open side ing force at the working element and hence, to jack up the
such that pressure oil delivered from the first and second body.
variable displacement hydraulic pumps is fed to the actuator
To achieve the above-described object, the present inven
via the third and fourth directional control valves and the
tion is also constructed, in an eighth aspect thereof. Such that
displacements of the first and second variable displacement in the hydraulic working machine of the above-described
hydraulic pumps are increasingly controlled by the Swash third or sixth construction, the flow-line changing means
comprises a flow control valve connected on an upstream side
angle instruction means.
In this construction, it is also possible to exhibit similar 25 of the third directional control valve to the meter-in port of the
advantageous effects as the above-described second means third directional control valve such that the flow control valve
for resolving the defects, that is, to produce a large pressing is changed over to a closed position when the jack-up selector
force at the working element while achieving a reduction in valve has been changed over to the first selected position and
the horse power consumption of the pump and an improve is changed over to an open position when the jack-up selector
ment in the energy efficiency of the hydraulic working 30 valve has been changed over to the second selected position,
machine upon performing a simple lowering operation of the and a center bypass selector valve connected on a downstream
working element, and further to smoothly effect a switchover side of the third directional control valve to a center bypass
from a simple lowering operation of the working element to a port of the third directional control valve such that the center
pressing operation of the working element. In addition, owing bypass selector valve is changed over to an open position
to the arrangement of the travelling hydraulic circuit, it is also 35 when the jack-up selector valve has been changed over to the
possible to jackup the body by performing a combined opera first selected position and is changed over to a closed position
tion of a traveling operation and a working-element-lowering when the jack-up selector valve has been changed over to the
operation.
second selected position.
To achieve the above-described object, the present inven
In this construction, it is also possible to exhibit similar
tion is also constructed, in a seventh aspect thereof. Such that 40 advantageous effects as the above-described third means for
in the hydraulic working machine of the above-described resolving the defects, that is, to achieve a reduction in the
first, second or fifth construction, the flow-line changing horsepower consumption of the pump and an improvement in
means comprises a flow control valve connected on an the energy efficiency of the hydraulic working machine upon
upstream side of the directional control valve to the meter-in performing a simple lowering operation of the working ele
port of the directional control valve such that the flow control 45 ment, and further to jack up the body by performing a com
valve is changed over to a closed position when the jack-up bined operation of a traveling operation and a working-ele
selector valve has been changed over to the first selected ment-lowering operation.
position and is changed over to an open position when the
To achieve the above-described object, the present inven
jack-up selector valve has been changed over to the second tion is also constructed, in a ninth aspect thereof. Such that in
selected position, and a center bypass selector valve con 50 the hydraulic working machine of any one of the above
nected on a downstream side of the directional control valve
described seventh to ninth constructions, the hydraulic work
to a center bypass port of the directional control valve such ing machine is provided with a hydraulically-piloted selector
that the center bypass selector valve is changed over to an valve as the jack-up selector valve, and the hydraulically
open position when the jack-up selector valve has been piloted selector valve is provided at a pilot port thereof with a
changed over to the first selected position and is changed over 55 restrictor.
When a hydraulically-piloted selector valve is arranged as
to a closed position when the jack-up selector valve has been
changed over to the second selected position.
the jack-up selector valve as described above, it is only nec
When the flow-line changing means in the first, second or essary to connect a signal port of the jack-up selector valve
fifth means for resolving the defects is constructed of a flow and the bottom chamber of the hydraulic cylinder with each
control valve and center bypass selector valve, which are 60 other via a line, so that the construction is simple. It is,
changed over depending on the selected position of the jack accordingly, possible to realize at low cost a hydraulic work
up selector valve, as described above, the flow control valve ing machine which can achieve a reduction in the horsepower
and center bypass selector valve are changed over to the consumption of the pump and an improvement in energy
closed position and the open position, respectively, when the efficiency upon performing a simple lowering operation of
jack-up selector valve has been changed over to the first 65 the working element and can also jack up the body. When the
selected position, in other words, when the working element hydraulically-piloted selector valve is provided at the pilot
falls by its own weight. As a result, the pressure oil delivered port thereof with a restrictor, it is possible to avoid hunting of
US 8,336,443 B2
10
the hydraulically-piloted selector valve, and hence, to rod chamber of the hydraulic cylinder for the boom even
smoothly and surely effect a switchover from a simple low when a pressing force is applied to the boom in the course of
ering operation of the working element to a pressing opera a simple lowering operation of the working element. It is,
therefore, possible to prevent the rod chamber of the hydrau
tion of the working element.
To achieve the above-described object, the present inven 5 lic cylinder for the boom from being brought into a vacuum
state to form a cavity, and hence, to continue a smooth opera
tion is also constructed, in a tenth aspect thereof. Such that in tion
of the boom.
the hydraulic working machine of any one of the above
It
is
to be noted that the terms “equal to or higher than the
described first to ninth constructions, the hydraulic working predetermined
pressure' and “lower than the predetermined
machine is further provided with a solenoid-operated selector pressure' as used
herein indicate the differentiation of situa
valve for performing a change-over control of the jack-up 10 tions into those higher
than the predetermined pressure as a
selector valve, a pressure sensing means for sensing a pres standard and those lower
than the predetermined pressure as
sure value in the bottom chamber of the hydraulic cylinder, the standard and are a matter
of design choice set as desired at
and an electric control means for operating the Solenoid the time of designing as to whether
the selected position of the
operated selector valve on a basis of a pressure sensed by the jack-up selector valve in the case of the predetermined pres
15
pressure sensing means.
sure should be set at the first selected position or at the second
When a solenoid-operated selector valve is arranged as the selected position.
jack-up selector valve as described above, it is possible to
When a hydraulically-piloted selector valve is arranged as
omitat least a line which connects the bottom chamber (hold the jack-up selector valve as described above, it is only nec
ing pressure side) of the hydraulic cylinder and the signal port essary to connect a signal port of the jack-up selector valve
of the jack-up selector valve with each other, thereby making and the bottom chamber of the hydraulic cylinder with each
it possible to achieve simplification of the hydraulic circuit.
other via a line, so that the construction is simple. It is,
To achieve the above-described object, the present inven accordingly, possible to realize at low cost a hydraulic work
tion is constructed, in an eleventh aspect thereof. Such that in ing machine which can achieve a reduction in the horsepower
the hydraulic working machine of the above-described fifth or consumption of the pump and an improvement in energy
sixth construction, a combination of plural shuttle valves, 25 efficiency upon performing a simple lowering operation of
which select a highest one of a predetermined group of con the working element and can also jack up the body.
When a solenoid-operated selector valve is arranged as the
trol signal pressures among control signal pressures produced
jack-up
selector valve as described above, it is possible to
by the pilot control unit, is used as the Swash angle instruction omitat least
a line which connects the bottom chamber of the
CaS.
hydraulic
cylinder
and the signal port of the jack-up selector
When a combination of plural shuttle valves is used as the 30
with each other, thereby making it possible to achieve
Swash angle instruction means as described above, a desired valve
simplification of the hydraulic circuit.
control signal pressure can be surely selected by a simple
As has been described above, the hydraulic working
circuit construction, thereby making it possible to realize at machine according to the present invention monitors changes
low cost a hydraulic working machine that increasingly con in the bottom pressure on the hydraulic cylinder which drives
trols the displacement of the variable displacement hydraulic 35 the working element and, when the bottom pressure on the
pump by the Swash angle instruction means upon performing hydraulic cylinder which drives the working element is equal
a pressing operation of the working element. When the high to or higher than the predetermined pressure upon lowering
est pressure is selected from the predetermined group of the working element, the jack-up selector valve is changed
control signal pressure by the Swash angle instruction means, over to the first selected position to change over the flow-line
pressure oil can be Surely fed as much as needed to the 40 changing means to the closed side such that the pressure oil
actuator upon performing a pressing operation of the working delivered from the main pump is not fed to the rod chamber of
element, thereby making it possible to Smoothly and Surely the hydraulic cylinder. Therefore, the horse power consump
effect a switchover from a simple lowering operation of the tion of the pump can be reduced upon performing a simple
working element to a pressing operation of the working ele lowering operation of the working element that does not
ment.
45 require any pressing force for jacking up the body and, when
To achieve the above-described object, the present inven a working element is operated in combination with allowing
tion is also constructed, in a twelfth aspect thereof. Such that another working element to fall, pressure oil to be fed to an
in the hydraulic working machine of each of the above-de actuator from the main pump to drive the first-mentioned
scribed constructions, the lowered working element is a working element can be relatively increased. Accordingly, the
boom, and the actuator is a hydraulic cylinder for the boom. 50 energy efficiency of the hydraulic working machine can be
When a boom and a hydraulic cylinder for the boom are improved. When the bottom pressure on the hydraulic cylin
arranged as the working element and the actuator, respec der is lower than the predetermined pressure upon lowering
tively, as described above, the hydraulic working machine the working element, on the other hand, the jack-up selector
such as a hydraulic excavator which is provided with the valve is changed over to the second selected position to
boom and the hydraulic cylinder for the boom can exhibit the 55 change over the flow-line changing means to the open side
advantageous effects described above with respect to the fifth such that the pressure oil delivered from the main pump is fed
and sixth means for resolving the defects.
to the rod chamber of the hydraulic cylinder via the direc
To achieve the above-described object, the present inven tional control valve. It is, therefore, possible to produce a
tion is also constructed, in a thirteenth aspect thereof. Such drive force for the working element as much as needed for
that in the hydraulic working machine of the above-described 60 jacking up the body and hence to jack up the body by per
twelfth construction, the hydraulic working machine is pro forming the combined operation of a traveling operation and
vided with a regeneration circuit for regenerating a portion of a lowering operation of the working element.
meter-out oil, which is discharged from a bottom chamber of
BRIEF DESCRIPTION OF THE DRAWINGS
the hydraulic cylinder for the boom, into meter-in oil to be fed
65
to a rod chamber of the hydraulic cylinder for the boom.
When a regeneration circuit is arranged as described
FIG. 1 is a side view of a hydraulic working machine
above, regenerated oil is fed from the bottom chamber to the according to the present invention.
US 8,336,443 B2
11
FIG. 2 is a circuit diagram of a hydraulic circuit according
to a first embodiment.
FIG. 3 is a construction diagram of a control unit.
FIG. 4 is a circuit diagram of a hydraulic circuit according
to a second embodiment.
FIG. 5 is a circuit diagram of a hydraulic circuit according
to a third embodiment.
FIG. 6 is a circuit diagram of a hydraulic circuit according
12
a change-over control of the directional control valve 22, a
pilot pump 24, a jack-up selector valve 25 for controlling a
flow of pressure oil delivered from the pilot pump 24, a flow
control valve 26 connected on an upstream side of the direc
tional control valve 22 to a meter-in port of the directional
control valve 22 such that the flow control valve is changed
over by the jack-up selector valve 25, a center bypass selector
valve 27 connected on a downstream side of the directional
control valve 22 to a center bypass port of the directional
FIG. 7 is a circuit diagram of a hydraulic circuit according 10 control valve 22 such that the center bypass selector valve is
to a fifth embodiment.
changed over by the jack-up selector valve 25, and a reservoir
FIG. 8 is a circuit diagram of a hydraulic circuit according 28. It is to be noted that the jack-up selector valve 25 is a
hydraulically-piloted selector valve changed over to commu
to a sixth embodiment.
FIG. 9 is a circuit diagram showing essential parts of a nicate pressure oil, which is delivered from the main pump
15 21, to the meter-inside upon performing a jack-up and that the
hydraulic circuit according to the sixth embodiment.
FIG.10 is a circuit diagram of a hydraulic circuit according center bypass selector valve 27 is a selector valve for opening
or closing the center bypass.
to a seventh embodiment.
It is also to be noted that the flow control valve 26 is
FIG.11 is a circuit diagram of a hydraulic circuit according
composed of a poppet valve 261 and a pilot-operated selector
to an eighth embodiment.
FIG. 12 is a circuit diagram of a hydraulic circuit according valve 262 for communicating a back pressure chamber of the
to a ninth embodiment.
poppet valve 261 and a pump port side of the directional
FIG. 13 is a circuit diagram of a hydraulic circuit according control valve 22 with each other or cutting them off from each
to a fourth embodiment.
to a tenth embodiment.
other.
Arranged as the directional control valve 22 is one having
FIG. 14 is a construction diagram of a shuttle valve group
arranged in the hydraulic circuit according to the tenth 25 a regeneration circuit, which is composed of restrictors 29a,
29b and a check valve 29C.
embodiment of the present invention.
As depicted in FIG. 3, the control unit 23 is constructed of
BEST MODES FOR CARRYING OUT THE
a control lever 23a, and a boom-lowering-side reducing valve
INVENTION
23b and boom-raising-side reducing valve 23c, which are
30 changed over by the control lever 23a.
(Outside Construction of Hydraulic Working Machine)
Arranged between the main pump 21 and the directional
Firstly, the outside construction of the hydraulic working control valve 22 are a line 31 directly communicating from
machine according to the present invention will be described the main pump 21 to the center bypassport of the directional
with reference to FIG.1. FIG. 1 is a side view of the hydraulic control valve 22 and lines 32.33 communicating from the
35 main pump 21 to the meter-in port of the directional control
working machine according to the present invention.
The hydraulic working machine illustrated by way of valve 22 via the flow control valve 26. Arranged between the
example is a hydraulic excavator, and as shown in FIG. 1, is directional control valve 22 and the hydraulic boom cylinder
primarily constructed of a travel base 3 composed of a pair of 11 are a line 35 communicating to the bottom chamber 11a
left and right track units 1.2, a Swing upperstructure 4 Swing and a line 35 communicating to the rod chamber 11b.
ably mounted on the travel base 3, a boom 5 pivotally pin 40 Between the bottom chamber 11a of the hydraulic boom
connected at an end thereof on the Swing upperstructure 4, an cylinder 11 and a signal port of the jack-up selector valve 25,
arm 6 pivotally pin-connected at an end thereof to the boom 5. a line 36 is arranged for feeding a bottom pressure signal. A
a bucket 7 pivotally pin-connected at an end thereof to the arm line which connects the directional control valve 22 and the
6, a first and second track motors 8.9 for driving the track units reservoir 28 with each other is divided, via the center bypass
1.2, a Swinging hydraulic motor 10 for driving the Swing 45 selector valve 27, into a line 37 on the side of the directional
upperstructure 4, a hydraulic boom cylinder 11 for driving the control valve 22 and a line 38 on the side of the reservoir 28,
boom 5, a hydraulic arm cylinder 12 for driving the arm 6, and and between the directional control valve 22 and the line 38
a hydraulic bucket cylinder 13 for driving the bucket 7.
on the side of the reservoir 28, a line 39 is arranged to guide
a portion of pressure oil, which is discharged from the bottom
(First Embodiment of the Hydraulic Circuit)
With reference to FIG. 2 and FIG.3, a description will next 50 chamber 11a, to the reservoir 28. Arranged between the con
be made of the first embodiment of the hydraulic circuit trol unit 23 and a signal port of the directional control valve 22
arranged on the hydraulic working machine. FIG. 2 is a frag are a pilot line 40 for feeding a boom-lowering signal and a
mentary circuit diagram of the hydraulic circuit according to pilot line 41 for feeding a boom-raising signal. Further,
the first embodiment, and FIG. 3 is a construction diagram of change-over signal feeding pilot lines 42.43 are arranged to
a control unit. As clearly seen from these figures, the hydrau 55 guide a boom-lowering pilot pressure to the center bypass
lic circuit according to this embodiment is characterized in selector valve 27 via the jack-up selector valve 25. In addi
that a hydraulically-piloted selector valve is arranged as a tion, between the pilot pump 24 and a signal port of the
jack-up selector valve and oil pressure from one main pump is selector valve 262 which constitutes the flow control valve 26,
fed to a hydraulic cylinder.
change-over signal feeding pilot lines 44.45 are arranged with
As illustrated in FIG. 2, the hydraulic circuit of this 60 the jack-up selector valve 25 interposed therebetween.
A description will hereinafter be made about operations of
embodiment is primarily constructed of a main pump 21, a
double-acting, hydraulic boom cylinder 11 arranged for the hydraulic working machine according to the first embodi
extension or contraction by pressure oil delivered from the ment constructed as described above.
When the control lever 23a is at a neutral position and no
main pump 21 to drive the boom 5, a directional control valve
22 for controlling flows of pressure oil to be fed from the main 65 pulling force is applied to the hydraulic boom cylinder 11, the
pump 21 to a bottom chamber 11a and rod chamber 11b of the directional control valve 22 assumes a neutral position 22b as
hydraulic boom cylinder 11, a control unit 23 for performing shown in FIG. 2. The bottom chamber 11a of the hydraulic
US 8,336,443 B2
14
13
boom cylinder 11 has a high pressure to support the dead chamber 11a, thereby making it possible to produce a strong
weight of the boom or the like, the jack-up selector valve 25 pressing force Such as a jack-up force for the body.
When the control lever 23a is operated in a rightward
is changed over to a selected position 25a, the selector valve
262 in the flow control valve 26 is changed over to a selected direction as viewed in the figure, that is, in a boom-raising
position 26a, and the center bypass selector valve 27 main 5 direction, a pilot pressure is outputted to the pilot line 41
tains a valve element position 27a. Accordingly, the pressure owing to the pressure oilfed from the pilot pump 24 so that the
oil delivered from the main pump 21 is guided to the reservoir directional control valve 22 is changed over to a selected
28 through the line 31, the center bypass port of the direc position 22c. As a result, the pressure oil discharged from the
chamber 11b is returned to the reservoir 28 through the
tional control valve 22, the line 37, the center bypass selector 10 rod
line 35, directional control valve 22 and line39. Accordingly,
valve 27 and the line 38.
bottom pressure becomes lower than the operating pres
When the control lever 23a is operated in a leftward direc the
sure
jack-up selector valve 25 so that the flow control
tion as viewed in the figure, that is, in a boom-lowering valvefor26the
is changed over to the selected position 26b. As a
direction in the above-described state, the pressure oil fed consequence, the pressure oil fed from the main pump 21 to
from the pilot pump 24 is reduced in pressure by the reducing 15 the meter-in port of the directional control valve 22 through
valve 23b, the resulting, pressure-reduced pilot pressure is the line 32, flow control valve 26 and line 33 is fed to the
outputted as a boom-lowering signal to the pilot line 40, and bottom chamber 11a through the line34. The hydraulic boom
the directional control valve 22 is changed over to a selected cylinder 11 is hence caused to extend so that the boom 5 is
position 22a. Further, a portion of return oil from the bottom caused to turn in the upward direction.
chamber 11a is regenerated in the rod chamber 11b via the
The hydraulic working machine according to this embodi
restrictor 29b, check valve 29c and line 35, and the rest of the
ment is designed to monitor changes in the bottom pressure of
return oil is returned to the reservoir 28 via the restrictor 29a
the hydraulic boom cylinder 11 and, when the bottom pres
and line 39.
sure on the hydraulic boom cylinder 11 is equal to or higher
When the bottom pressure is higher than a predetermined than the predetermined pressure upon lowering the boom, to
change-over pressure set by a spring 25c of the jack-up selec 25 change over the jack-up selector valve 25 to the selected
position 25a, and accordingly, to change over the selector
tor valve 25 in the above-described situation, the selected
position of the jack-up selector valve 25 is maintained at the valve 262 in the flow control valve 26 to the selected position
selected position 25a, so that the selected position of the flow 26a and the center bypass selector valve 27 to the valve
control valve 26 is also maintained at the selected position element position 27a such that the pressure oil delivered from
26a and the center bypass selector valve 27 is also maintained 30 the main pump 21 is not fed to the rod chamber 11b of the
at the valve element position 27a. Accordingly, the pressure hydraulic boom cylinder 11. It is, therefore, possible to
oil delivered from the main pump 21 is guided to the reservoir reduce the horse power consumption of the pump upon per
28 through the line 31, the center bypass port of the direc forming a simple boom-lowering operation which does not
tional control valve 22, the line 37, the center bypass selector require a pressing force for jacking up the body. As the pres
valve 27 and the line 38 and the pressure oil is fed neither to 35 sure oil delivered from the main pump 21 is not fed to the rod
the bottom chamber 11a nor the rod chamber 11b of the
chamber 11 of the hydraulic boom cylinder 11 upon perform
hydraulic boom cylinder 11. Therefore, only the regenerated ing a simple boom-lowering operation, it is possible to rela
oil is introduced into the rod chamber 11b, the hydraulic tively increase the pressure oil to be fed from the main pump
boom cylinder 11 contracts under the dead weight of the 21 to the hydraulic arm cylinder 12 and hydraulic bucket
boom 5, and the boom 5 is caused to turn in a downward 40 cylinder 13 upon operating the boom 5 in combination with
one or more other working elements, for example, the arm 6
direction (undergoes a so-called free fall).
When the bottom pressure is lower than the change-over and/or bucket 7. This makes it possible to improve the energy
pressure for the jack-up selector valve 25 in the situation that efficiency of the hydraulic working machine. When the bot
the control lever 23a has been operated in the boom-lowering tom pressure on the hydraulic boom cylinder 11 is lower than
direction, on the other hand, the jack-up selector valve 25 is 45 the predetermined pressure upon lowering the boom, on the
changed over to a selected position 25b, and the pressure oil, other hand, the jack-up selector valve 25 is changed over to
which has been fed from the pilot pump 24 to the signal port the selected position 25b, and as a result, the selector valve
of the selector valve 262 in the flow control valve 26 via the
262 in the flow control valve 26 is changed over to the selected
pilot line 44 and pilot line 45, is cut off. Accordingly, the position 26b and the center bypass selector valve 27 is
selector valve 262 is changed over to a selected position 26b, 50 changed over to the valve element position 27b such that the
the back pressure on the poppet valve 261 becomes equal to pressure oil delivered from the main pump 21 is fed to the rod
the pressure in the line33, and the pressure oil delivered from chamber 11b of the hydraulic boom cylinder 11. It is, there
the main pump 21 is fed to the meter-in port of the directional fore, possible to produce a large pressing force at the boom 5
control valve 22 through the line 32, the poppet valve 261 in and to jack up the body.
the flow control valve 26, and the line 33. Responsive to a 55 The hydraulic working machine according to this embodi
change-over of the jack-up selector valve 25, the pressure oil ment uses, as the directional control valve 22, the regenera
delivered from the pilot pump 24 is fed to the signal port of the tion circuit composed of the restrictors 29a,29b and the check
center bypass selector valve 27through the pilot line 40, pilot valve 29c. Even when a pressing force is applied to the boom
line 42, jack-up selector valve 25 and pilot line 43. As a 5 in the course of a simple boom-lowering operation, the
consequence, the center bypass selector valve 27 is changed 60 regenerated oil from the bottom chamber 11a can, therefore,
over to a selected position 27b so that the downstream of the be fed to the rod chamber 11b of the hydraulic boom cylinder
11, thereby making it possible to prevent the rod chamber 11b
center bypass of the directional control valve 22 is cut off.
Accordingly, the pressure oil from the main pump 21, said of the hydraulic boom cylinder 11 from being brought into a
pressure oil having been fed from the line 33 to the meter-in vacuum state to form a cavity and hence to continue a Smooth
port of the directional control valve 2, is fed to the rod cham 65 operation of the boom 5.
As the hydraulic working machine according to this
ber 11b of the hydraulic boom cylinder 11 through the line 35
together with the regenerated oil discharged form the boom embodiment is also provided with a hydraulically-piloted
US 8,336,443 B2
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16
selector valve as the jack-up selector valve 25, it is only retains the valve element position 27a, the pressure oil to be
necessary to connect the signal port of the jack-up selector fed to the rod chamber 11b consists solely of the regenerated
valve 25 and the bottom chamber 11a of the hydraulic boom oil discharged from the bottom chamber 11a and the boom 5
cylinder 11 with each other via the line 36, so that the con undergoes a free fall, as described in connection with the first
struction is simple. It is, accordingly, possible to realize at low 5 embodiment. When the jack-up selector valve 25 has been
costa hydraulic working machine which can achieve a reduc changed over to the selected position 25b and the center
tion in the horse power consumption of the pump and an bypass selector valve 27 has been changed over to the selected
improvement in energy efficiency upon performing a simple position 27b, on the other hand, the regenerated oil and the
boom-lowering operation and can also jack up the body.
pressure oil fed from the main pump 21 are combined and fed
10 to the rod chamber 11b and a strong pressing force such as a
(Second Embodiment of the Hydraulic Circuit)
With reference to FIG.4, a description will next be made of jack-up force for the body can be obtained, as described in
the second embodiment of the hydraulic circuit arranged on connection with the first embodiment.
The hydraulic working machine according to this embodi
the hydraulic working machine. FIG. 4 is a circuit diagram of
the hydraulic circuit according to the second embodiment, ment can bring about similar advantageous effects as the
and as clearly seen from this figure, the hydraulic circuit of 15 hydraulic working machine according to the first embodi
this embodiment is characterized in that change-over controls ment. In addition, it can omitat least the line which connects
of the jack-up selector valve and center bypass selector valve the bottom chamber 11a of the hydraulic boom cylinder 11
are performed by a solenoid valve.
and the signal port of the jack-up selector valve 25 with each
In FIG.4, reference numeral 51 indicates a pressure sensor other, thereby making it possible to achieve simplification of
for sensing a bottom pressure on the hydraulic boom cylinder the hydraulic circuit.
11, reference numeral 52 a solenoid valve for changing over (Third Embodiment of the Hydraulic Circuit)
the jack-up selector valve 25 and center bypass selector valve
With reference to FIG. 5, a description will next be made of
27, reference numeral 53 a controller for receiving an output the third embodiment of the hydraulic circuit arranged on the
signal from the pressure sensor 51 and outputting an instruc hydraulic working machine. FIG. 5 is a circuit diagram of the
tion current value to be fed to a signal input part of the 25 hydraulic circuit according to the third embodiment, and as
solenoid valve 52, reference numeral 54 a line branching out clearly seen from this figure, the hydraulic circuit of this
from the pilot line 40 and communicating to the Solenoid embodiment is characterized in that two solenoid valves are
valve 52, reference numeral 55 a pilot line connecting the arranged as a jack-up selector valve, and change-over con
signal port of the jack-up selector valve 25 and the solenoid trols of these two solenoid valves are performed based on the
valve 52 with each other, and reference numeral 56 a pilot line 30 bottom pressure on the hydraulic boom cylinder and the pilot
connecting the signal port of the center bypass selector valve pressure to the directional control valve.
27 and the solenoid valve 52 with each other. Other elements
In FIG. 5, reference numeral 51 indicates a first pressure
which are the same or equivalent to corresponding elements sensor for sensing a bottom pressure on the hydraulic boom
cylinder 11, reference numerals 61.62 a first and second sole
in FIG. 2 are shown by the same reference numerals.
Stored in the controller 53 is a relationship between the 35 noid valves which make up the jack-up selector valve, refer
values of bottom pressures on the hydraulic boom cylinder 11 ence numeral 63 a second pressure sensor for sensing a pilot
as detected by the pressure sensor 51 and instruction current pressure in the pilot line 40, reference numeral 64 a controller
values to be fed to the signal input part of the solenoid valve for receiving an output signal from the first pressure sensor 51
52. When a bottom pressure value detected by the pressure and an output signal from the second pressure sensor 63 and
sensor 51 is within a range of bottom pressure values upon 40 outputting instruction current values to change over the
free falling of the boom, namely, is equal to or higher than a selected positions of the first and second solenoid valves
predetermined pressure P0, the solenoid valve 52 retains a 61,62, reference numeral 65 a pilot line connecting the first
valve element position 52a. When a bottom pressure value solenoid valve 61 and the signal port of the selector valve 262
detected by the pressure sensor 51 is within a range of bottom in the flow control valve 26 with each other, and reference
pressures in the situations that pressing forces are applied to 45 numeral 66 a pilot line connecting the second Solenoid valve
the boom 5, namely, is lower than the predetermined pressure 62 and the signal port of the center bypass selector valve 27
P0, on the other hand, an instruction current is outputted to with each other. Other elements which are the same or equiva
lent to corresponding elements in FIG. 2 are shown by the
change over the solenoid valve 52 to a selected position 52b.
When the solenoid valve 52 retains the valve element posi same reference numerals.
tion 52a, a pilot pressure which serves as a boom-lowering 50 The controller 64 is constructed, as depicted in FIG. 5, of a
signal is cut off at the solenoid valve 52 and no pilot pressure first storage unit 71 in which a relationship between the values
arises in the pilot lines 55.56. Accordingly, the jack-up selec of bottom pressures (BM/B pressures) on the hydraulic boom
tor valve 25 retains the valve element position 25a, so that the cylinder 11 as sensed by the first pressure sensor 51 and
selector valve 262 in the flow control valve 26 is changed over instruction current values to be fed to signal input parts of the
to the selected position 26a and the center bypass selector 55 first and second solenoid valves 61,62 is stored, a second
valve 27 retains the valve element position 27a. When the storage unit 72 in which a relationship between pilot pres
solenoid valve 52 is changed over to the selected position 52b Sures (boom-lowering signals) in the pilot line 40 as sensed by
to perform a boom operation, on the other hand, a pilot pres the second pressure sensor 63 and instruction current values
Sure which serves as a boom-lowering signal is fed to the pilot to be fed to the signal input part of the first solenoid valve 62
lines 55.56 via the solenoid valve 52. Accordingly, the jack 60 is stored, and a lowest selection circuit 73 for selecting the
up selector valve 25 is changed over to the selected position lower one of an instruction current value outputted from the
first storage unit 71 and an instruction current value outputted
25b, so that the selector valve 262 in the flow control valve 26
is changed over to the selected position 26b and the center from the second storage unit 72 and feeding it to the signal
bypass selector valve 27 is changed over to the selected posi input part of the first solenoid value 62.
tion 27b.
65
According to the controller 64 in this embodiment, when
When the selector valve 262 has been changed over to the the value of a bottom pressure on the hydraulic boom cylinder
selected position 26a and the center bypass selector valve 27 11 as sensed by the pressure sensor 51 is within the range of
US 8,336,443 B2
17
bottom pressure values upon freefalling of the boom, namely,
is equal to or higher than the predetermined pressure P0, an
instruction current value outputted from the first storage unit
18
unit 71 has a large value and an instruction current value pi
outputted from the second storage unit 72 has a small value.
The Smaller one of these instruction current values pi is,
71 is a small value so that the first solenoid valve 61 retains a
therefore, outputted from the smaller selection circuit 73 so
valve element position 61a, and irrespective of the level of an that the center bypass selector valve 27 is not changed over
instruction current outputted from the second storage unit 72, while retaining the selected position 27a. Accordingly, if the
the instruction current of the small value is outputted from the center bypass selector valve 27 is changed over to the selected
position 27b before the first solenoid valve 61 is changed over
lowest selection circuit 73. Therefore, the second solenoid
valve 62 also retains a valve element position 62a. As the to the selected position 61b, the delivery pressure from the
pressure oil delivered from the pilot pump 24 is hence fed to 10 pump wastefully increases, leading to a deterioration in
the signal port of the selector valve 262 in the flow control energy efficiency.
The hydraulic working machine according to this embodi
valve 26 via the first solenoid valve 61 and the pilot line 65,
the selector valve 262 is changed over to the selected position ment can also bring about similar advantageous effects as the
26a. Further, the pressure oil delivered from the pilot pump 24 hydraulic working machine according to the second embodi
is cut off at the second solenoid valve 62, so that no pilot 15 ment.
pressure arises in the pilot line 66 and the center bypass (Fourth Embodiment of the Hydraulic Circuit)
With reference to FIG. 6, a description will next be made of
selector valve 27 retains the valve element position 27a.
When the value of a bottom pressure on the hydraulic boom the fourth embodiment of the hydraulic circuit arranged on
cylinder 11 as sensed by the pressure sensor 51 is within the the hydraulic working machine. FIG. 6 is a circuit diagram of
range of bottom pressure values in situations that pressing the hydraulic circuit according to the fourth embodiment, and
forces are applied to the boom 5, namely, is lower than the as clearly seen from this figure, the hydraulic circuit of this
predetermined pressure P0, an instruction current value out embodiment is characterized in that change-over controls of
putted from the first storage unit 71 is a large value so that the the directional control valve 22, flow control valve 26 and
first solenoid valve 61 is changed over to the selected position center bypass selector valve 27 are performed by a pilot
61b. From the lowest selection circuit 73, a current corre 25 pressure reduced in pressure by the reducing valve 23b con
sponding to an instruction current outputted from the second stituting the control unit 23, namely, a boom-lowering signal.
storage unit 72 is also outputted. When a boom-lowering
In FIG. 6, reference numeral 51 indicates the first pressure
operation is performed, the second solenoid valve 62 and the sensor for sensing a bottom pressure on the hydraulic boom
center bypass selector valve 27 are, therefore, changed overto cylinder 11, reference numerals 81.82 a first and second sole
a selected position 62b and the selected position 27b, respec 30 noid valves which make up the jack-up selector valve, refer
tively. When no boom-lowering operation is performed, on ence numeral 83 a controller for receiving an output signal
from the first pressure sensor 51 and outputting instruction
the other hand, the second solenoid valve 62 retains the valve
element position 62a so that the center bypass selector valve current values to change over the selected positions of the first
and second solenoid valves 81,82, reference numeral 84 a
27 retains the valve element position 27a.
When the selector valve 262 in the flow control valve 26 35 pilot line branching out from the pilot line 40 and connecting
has been changed over to the selected position 26a and the it to the first solenoid valve 81, reference numeral 85a pilot
center bypass selector valve 27 retains the valve element line branching out from the pilot line 40 and connecting it to
position 27a, only the regenerated oil discharged from the the second solenoid valve 82, reference numeral 86 a pilot
bottom chamber 11a is fed to the rod chamber 11b and the
line connecting the first Solenoid valve 81 and the signal port
boom 5 undergoes a free fall, as described in connection with 40 of the selector valve 262 in the flow control valve 26 with each
the first embodiment. When the valve element positions of the other, reference numeral 87 a pilot line connecting the second
solenoid valve 82 and the signal port of the center bypass
first solenoid valve 61 and second solenoid valve 62, which
make up the jack-up selector valve 25, have been changed selector valve 27 with each other, reference numeral 88 a pilot
over to the selected positions 61b,62b, respectively, and the line connecting the second solenoid valve 82 and the boom
center bypass selector valve 27 has been changed over to the 45 raising, reducing valve 23c arranged in the control unit 23
selected position 27b, on the other hand, the regenerated oil with each other, and numeral 89 a check valve arranged at a
and the pressure oil fed from the main pump 21 are combined point of connection between the pilot line 87 and the pilot line
and fed to the rod chamber 11b and a strong pressing force 88. Other elements which are the same or equivalent to cor
Such as a jack-up force for the body is produced, as described responding elements in FIG. 2 are shown by the same refer
in connection with the first embodiment.
50
ence numerals.
The controller 83 is constructed, as depicted in FIG. 6, of a
It is to be noted that the first and second storage units 71.72
have different characteristics as also appreciated from FIG. 5, first storage unit 91 in which a relationship between the values
because the jack-up selector valve 25 and the center bypass of bottom pressures on the hydraulic boom cylinder 11 as
selector valve 27 are in Such a relationship as being indepen sensed by the first pressure sensor 51 and an instruction
dently changed over in the third embodiment as opposed to 55 current value to be fed to a signal input part of the first
the above-mentioned first and second embodiments in each of
solenoid valve 81 is stored, and a second storage unit 92 in
which the jack-up selector valve 25 and the center bypass which a relationship between the values of bottom pressures
selector valve 27 are in Such a relationship as being changed on the hydraulic boom cylinder 11 as sensed by the first
over in an interlocked manner. As mentioned above, when the
pressure sensor 51 and an instruction current value to be fed
boom bottom pressure is lower than P0 in the first memory 60 to a signal input part of the second Solenoid valve 82 is stored.
unit 71, the first solenoid valve 61 which constitutes the
It is to be noted that concerning the instruction current values,
jack-up selector valve 25 is changed over to the selected standard current values are set in advance and the thus-set
position 61b no matter whether or not a boom-lowering current values are used as the instruction current values.
operation is performed.
According to the controller 83 in this embodiment, when
When the boom bottom pressure is lower than P0 and no 65 the value of a bottom pressure on the hydraulic boom cylinder
boom-lowering operation is performed, on the other hand, an 11 as sensed by the pressure sensor 51 is within the range of
instruction current value pi outputted from the first storage bottom pressure values upon freefalling of the boom, namely,
US 8,336,443 B2
19
is equal to or higher than the predetermined pressure P0, the
first solenoid value 81 retains a valve element position 81a by
an instruction current value outputted from the first storage
20
unit 92. The selector valve 262 is, therefore, changed over
before the center bypass selector valve 27. By changing over
the jack-up selector valve 25 before the center bypass selector
unit 91 and the second solenoid valve 82 retains a valve
valve 27 as described above, the fourth embodiment can be
element position 82a by an instruction current value output operated with good energy efficiency like the third embodi
ment.
ted from the second storage unit 92. When a boom-lowering
operation is performed, a boom-lowering pilot pressure is fed
The hydraulic working machine according to this embodi
from the pilot line 40 to the signal port of the selector valve ment can also bring about similar advantageous effects as the
262 in the flow control valve 26 through the pilot line 84, first hydraulic working machine according to the second embodi
solenoid valve 81 and pilot line 86, so that the selector valve 10 ment.
262 is changed over to the selected position 26a and the pilot (Fifth Embodiment of the Hydraulic Circuit)
line 85 is cut off at the second solenoid valve 82. As a conse
With reference to FIG. 7, a description will next be made of
quence, no pilot pressure arises in the pilot line 87 and the the fifth embodiment of the hydraulic circuit arranged on the
center bypass selector valve 27 retains the valve element hydraulic working machine. FIG. 7 is a circuit diagram of the
15 hydraulic circuit according to the fifth embodiment, and as
position 27a.
When the value of a bottom pressure on the hydraulic boom clearly seen from this figure, the hydraulic circuit of this
cylinder 11 as sensed by the pressure sensor 51 is within the embodiment is characterized in that a track-unit-driving,
range of bottom pressure values in situations that pressing hydraulic circuit is combined with a boom-driving, hydraulic
forces are applied to the boom 5, namely, is lower than the circuit.
predetermined pressure P0, the first solenoid valve 81 is
In FIG. 7, reference numeral 8 indicates a right-track
changed over to a selected position 81b by an instruction hydraulic motor, reference numeral 9 a left-track hydraulic
current value outputted from the first storage unit 91 and the motor, reference numeral 101 a second main pump, reference
second Solenoid valve 82 is changed over to a selected posi numeral 102 a second directional control valve for controlling
tion 82b by an instruction current value outputted from the a flow of pressure oil to be fed from the main pump 21 to the
second storage unit 92. The pilot line 84 is, therefore, cut off 25 right-track hydraulic motor 8, reference numeral 103 a third
at the first solenoid valve 81. Accordingly, no pilot pressure directional control valve for controlling a flow of pressure oil
arises in the pilot line 86, the flow control valve 26 is changed to be fed from the second main pump 101 to the left-track
over to the selected position 26b, and the pilot line 40 and the hydraulic motor 9, reference numeral 104 a fourth directional
pilot line 87 are brought into a state communicated with each control valve for controlling a flow of pressure oil to be fed
other. When a boom-lowering operation is performed, a 30 from the second main pump 101 to the hydraulic boom cyl
boom-lowering pilot pressure is, therefore, fed to the signal inder 11, reference numeral 105 a selector valve for feeding
port of the center bypass selector valve 27 through the pilot the pressure oil, which is fed from the first main pump 21, to
line 40, pilot line 85, second solenoid valve 82 and the pilot the side of the left-track hydraulic motor 9 upon performing a
line 87. As a consequence, the center bypass selector valve 27 boom-lowering operation, reference numeral 106 a shuttle
35 valve for applying a change-over signal to the selector valve
is changed over to the selected position 27b.
When the selector valve 262 in the flow control valve 26
105 when a boom operation has been performed, reference
has been changed over to the selected position 26a and the numeral 107 a line connecting the second main pump 101 and
center bypass selector valve 27 has been changed over to the the fourth directional control valve 104 with each other, ref
selected position 27a, only the regenerated oil discharged erence numeral 108 a center bypass passage connecting the
from the bottom chamber 11a is fed to the rod chamber 11b 40 second main pump 101 and the reservoir 28 with each other,
and the boom 5 undergoes a free fall, as described in connec reference numeral 109 a line connecting the fourth directional
tion with the first embodiment. When the first solenoid valve
control valve 104 and the rod chamber 11b of the hydraulic
81 and second solenoid valve 82, which make up the jack-up boom cylinder 11 with each other, reference numeral 110 a
selector valve 25, have been changed over to the selected line connecting the fourth directional control valve 104 and
positions 81b,82b, respectively, and the center bypass selec 45 the bottom chamber 11a of the hydraulic boom cylinder 11
tor valve 27 has been changed over to the selected position with each other, reference numeral 111 a check valve
27b, on the other hand, the regenerated oil and the pressure oil arranged on the line 110, reference numeral 112 a line con
fed from the main pump 21 are combined and fed to the rod necting the main pump 21 and the selector valve 105 with
chamber 11b and a strong pressing force Such as a jack-up each other, reference numeral 113 a check valve arranged on
force for the body is produced, as described in connection 50 the line 112, reference numeral 114 a line connecting the
with the first embodiment.
Selector valve 105 and the third directional control valve 103
with each other, reference numeral 115 a pilot line guiding a
also have different characteristics in this embodiment as in
pilot pressure, which serves as a boom-lowering signal, to the
the above-described third embodiment, because as in the third jack-up selector valve 25, reference numeral 116 a pilot line
embodiment, the jack-up selector valve 25 and the center 55 for feeding a boom-lowering signal to the signal port of the
bypass selector valve 27 are in Such a relationship as being fourth directional control valve 104, reference numeral 117 a
independently changed over. Especially in this embodiment, pilot line for feeding a boom-raising signal to the signal port
the change-over timings of the jack-up selector valve 25 and of the fourth directional control valve 104, and reference
center bypass selector valve 27 can be set different from each numeral 118 a pilot line for feeding a change-over signal to
other by providing the two storage units with different char 60 the signal port of the selector valve 105. Other elements
acteristics. For example, taking a look at the relationship in which are the same or equivalent to corresponding elements
characteristics as illustrated in FIG. 6, their characteristics are
in FIG. 2 are shown by the same reference numerals.
A description will hereinafter be made about operations of
designed such that, when the boom bottom pressure (BM/B
pressure) becomes lower than the preset pressure Po as the the hydraulic working machine according to the fifth embodi
standard, in other words, has a value Smaller than the preset 65 ment constructed as described above.
value Po, an instruction pressure Pi is outputted from the first
When the control lever 23a is at the neutral position, the
storage unit 91 before it is outputted from the second storage directional control valve 22 and the fourth directional control
It is to be noted that the first and second storage units 91.92
US 8,336,443 B2
21
valve 104 retain the neutral position 22b and the neutral
position 104b, respectively, as illustrated in FIG. 7. Accord
ingly, the jack-up selector valve 25 is changed over to the
selected position 25a by the bottom-side pressure of the
hydraulic boom cylinder 11. In this state, the pilot line 43 is in
bypass selector valve 27 retains the valve element position
22
selector valve 27 through the pilot line 115, jack-up selector
valve 25 and pilot line 43. As a consequence, the center
bypass selector valve 27 is changed over to the selected posi
tion 27b, the center bypass selector valve 27 is changed over
to the selected position 27b, and the boom-lowering signal is
also fed to the signal port on the boom-lowering side of the
fourth directional control valve 104 through the pilot line 116.
27a and the selector valve 105 retains the valve element
The fourth directional control valve 104 is, therefore,
communication with the reservoir 28, so that the center
position 105a. Accordingly, the pressure oil delivered from changed over to a selected position 104a. Accordingly, the
the main pump 21 is guided to the reservoir 28 through the 10 pressure oil delivered from the main pump 21 is fed to the rod
line 31, the center bypass port of the directional control valve chamber 11b of the hydraulic boom cylinder 11, the pressure
22, the line37, the center bypass selector valve 27 and the line oil delivered from the second main pump 101 is fed to the rod
38. Further, the pressure oil delivered from the second main chamber 11b of the hydraulic boom cylinder 11 through the
pump 101 is guided to the reservoir 28 through the line 107. fourth directional control valve 104, line 109 and line 35, and
the line 108 and the center bypassport of the third directional 15 the regenerated oil discharged from the bottom chamber 11a,
control valve 103. No pressure oil is, therefore, fed to the the pressure oil fed from the main pump 21 and the pressure
bottom chamber 11a and rod chamber 11b of the hydraulic oil fed from the second main pump 101 are combined and fed
bottom cylinder 11.
to the rod chamber 11b. It is hence possible to produce a
When the control lever 23a is operated in a leftward direc strong pressing force like a jack-up force for the body.
Further, the boom-operating pilot pressure is guided to the
tion as viewed in the figure, that is, in a boom-lowering
direction in the above-described state, the pilot pressure Selector valve 105 via the shuttle valve 106 and line 118.
which has been fed from the pilot pump 24 and reduced in Accordingly, the selector valve 105 is changed over to a
pressure by the reducing valve 23b is outputted to the pilot selected position 105b, so that the pressure oil delivered from
line 40, and the directional control valve 22 is changed over to the main pump 21 is fed to the left-track and right-track
the selected position 22a. Further, this pilot pressure is guided 25 hydraulic motors 8.9 via the second directional control valve
to the pilot line 115 and then to the signal port of the selector 102 and third directional control valve 103, respectively. As a
valve 262 via the jack-up selector valve 25, so that the selector consequence, when the boom and the tracks are operated at
valve 262 is changed over to the selected position 26a. As a the same time, the pressure oil from the main pump 21 is fed
consequence, a portion of the return oil from the bottom to the left-track and right-track motors 8.9 and the pressure oil
chamber 11a is regenerated in the rod chamber 11b via the 30 from the second main pump 101 is fed to the hydraulic boom
cylinder 11, thereby making it possible to jack up the body by
restrictor 29b, check valve 29c and line 35, and the rest of the
return oil is returned to the reservoir 28 via the restrictor 29a
the combined operation of the track operation and the boom
and line 39.
lowering operation.
It is to be noted that, although a hydraulically-piloted selec
When the bottom pressure is higher than the operating
pressure for the jack-up selector valve 25 in the above-de 35 tor valve was used as the jack-up selector valve 25 in the
scribed situation, the jack-up selector valve 25 is maintained above-described fifth embodiment, an electrohydraulic or
at the selected position 25a, so that the selected position of the Solenoid-operated selector valve can also be used as in the
flow control valve 26 is also maintained at the selected posi hydraulic working machines according to the second to
tion 26a and the center bypass selector valve 27 is also main fourth embodiments.
tained at the valve element position 27a. Accordingly, the 40 (Sixth Embodiment of the Hydraulic Circuit)
pressure oil delivered from the main pump 21 is guided to the
With reference to FIG. 8 and FIG.9, a description will next
reservoir 28 through the line 31, the center bypassport of the be made of the sixth embodiment of the hydraulic circuit
directional control valve 22, the line 37, the center bypass arranged on the hydraulic working machine. FIG. 8 is a frag
selector valve 27 and the line 38, and the pressure oil deliv mentary circuit diagram of the hydraulic circuit according to
ered from the second main pump 101 is guided to the reser 45 the sixth embodiment, and FIG.9 is a construction diagram of
voir 28 through the line 107, the line 108 and the center a shuttle valve group arranged in the hydraulic circuit of the
bypass port of the third directional control valve 103. As a sixth embodiment. As clearly seen from these figures, the
consequence, the pressure oil is fed neither to the bottom hydraulic circuit of this embodiment is characterized in that a
chamber 11a nor the rod chamber 11b of the hydraulic boom hydraulically-piloted selector valve is arranged as a jack-up
cylinder 11. Therefore, only the regenerated oil discharged 50 selector valve and oil pressure from one variable displace
ment hydraulic pump is fed to a hydraulic cylinder.
from the bottom chamber 11a is fed to the rod chamber 11b,
the hydraulic boom cylinder 11 contracts under the dead
Different from the first embodiment shown in FIG. 2, the
hydraulic circuit of this embodiment is primarily constructed,
weight of the boom 5, and the boom 5 undergoes a free fall.
When the bottom pressure becomes lower than the operat as illustrated in FIG.2, of the variable displacement hydraulic
ing pressure for the jack-up selector valve 25 in the situation 55 pump (main pump) 21, a regulator (Swash angle control
that the control lever 23a has been operated in the boom means) 21a for controlling the displacement of the variable
lowering direction, on the other hand, the jack-up selector displacement hydraulic pump 21, the double-acting hydraulic
valve 25 is changed over to the selected position 25b, so that cylinder 11 arranged for extension or contraction by the pres
the pilot line 45 is brought into communication with the sure oil, which is delivered from the variable displacement
reservoir 28 via the jack-up selector valve 25 and the selector 60 hydraulic pump 21, to drive the boom (working element) 5,
valve 262 in the flow control valve 26 is changed over to the the directional control valve 22 for controlling flows of pres
valve element position 26b. The pressure oil delivered from sure oil to be fed from the variable displacement hydraulic
the main pump 21 is, therefore, fed to the meter-in port of the pump 21 to the bottom chamber 11a and rod changer 11b of
directional control valve 22 through the line 32, the flow the hydraulic boom cylinder (actuator) 11, the pilot control
control valve 26 and the line 33. Responsive to a change-over 65 unit 23 for performing a change-over control of the direc
of the jack-up selector valve 25, the pilot pressure is fed as a tional control valve 22, the pilot pump 24, the jack-up selector
boom-lowering signal to the signal port of the center bypass valve 25 for controlling a flow of pressure oil delivered from
US 8,336,443 B2
24
shuttle valve 303 in the first stage and the shuttle valve 309 in
the second stage, respectively, and the shuttle valve 312
selects the higher one of the control signal pressures selected
by the shuttle valve 309 and shuttle valve 310 in the second
selector valve 27 connected on the downstream side of the
stage, respectively.
The shuttle valves 313,314 are arranged in a fourth stage of
directional control valve 22 to the center bypass port of the
directional control valve 22 and change-over controlled by the shuttle valve group 30. The shuttle valve 313 selects the
the jack-up selector valve 25, the reservoir 28, and a shuttle higher one of the control signal pressures selected by the
valve group (Swash angle instruction means) 30 for output shuttle valve 301 in the first stage and the shuttle valve 311 in
ting Swash angle control signals to the regulator 21a in 10 the third stage, respectively, and the shuttle valve 304 selects
response to signals from the pilot control unit 23 and another the higher one of the control signal pressures selected by the
pilot control unit (not shown)
shuttle valve 311 and shuttle valve 312 in the third stage,
Arranged as the directional control valve 22 is one having respectively.
the regeneration circuit, which is composed of the restrictors
The shuttle valve 315 is arranged in a fifth stage of the
15 shuttle valve group 30, and selects the higher one of the
29a,29b and the check valve 29c.
As depicted in FIG. 3, the pilot control unit 23 is con control signal pressure selected by the shuttle valve 314 in the
structed of the control lever 23a, and the boom-lowering-side fourth stage and the boom-lowering control signal pressure
reducing valve 23b and boom-raising-side reducing valve Dd.
The hydraulic selector valve 317 is a proportional reducing
23c, which are changed over by the control lever 23a.
The jack-up selector valve 25 is provided at the pilot port valve which, based on the highest pressure selected at the
shuttle valve 313 and guided to a pressure-receiving part
thereof with an anti-hunting restrictor 25d.
The flow control valve 26 is composed of the poppet valve 317a, is operated to produce a control signal pressure (pump
261 and the pilot-operated selector valve 262 for communi control signal Xp1) from the pressure of the pilot pump 24.
cating the back pressure chamber of the poppet valve 261 and When the highest pressure selected at the shuttle valve 313 is
the pump port side of the directional control valve 22 with 25 lower than the reservoir pressure, this hydraulic selector valve
317 is at the position indicated in the figure to reduce the
each other or cutting them off from each other.
The shuttle valve group 30 is constructed, as depicted in control signal pressure to the reservoir pressure. When the
highest pressure selected at the shuttle valve 313 becomes
FIG. 9, of a combination of shuttle valves 301-315 and
hydraulic selector valves 317,318. It is to be noted that as the equal to or higher than the reservoir pressure, on the other
shuttle valve group 30, the individual shuttle valves and 30 hand, the hydraulic selector valve 317 is changed over from
hydraulic selector valves connected together through lines the position indicated in the figure, and outputs the pressure of
can be used or a block with the required shuttle valves and the pilot pump 24 after reducing it to a control signal pressure
hydraulic selector valves integrally assembled therein can corresponding to the level of the highest pressure. The regu
also be used.
lator 21a for the variable displacement hydraulic pump 21 is
Among the shuttle valves 301-315, the shuttle valves 301 35 operated by the control signal pressure (pump control signal
307 are arranged in a first stage of the shuttle valve group 30. Xp1).
The shuttle valve 301 selects the higher one of a right-track
The regulator 21a has a characteristic that it increases the
forward control signal pressure Afand a right-track rearward Swash angle of the variable displacement hydraulic pump 21
control signal pressure Ar, the shuttle valve 302 selects the as the pressure of the pump control signal Xp1 rises, and,
higher one of a left-track forward control signal pressure Bf 40 when a pump control signal Xp1 is applied, the regulator 21a
and a left-track rearward control signal pressure Br, the increases or decreases the delivery rate of the variable dis
shuttle valve 303 selects the higher one of a bucket-crowding placement hydraulic pump 21 depending on the pump control
control signal pressure Cc and a bucket-dumping control signal Xp1. Accordingly, when the pilot control unit 23 is
signal pressure Cd, the shuttle valve 304 selects the higher operated, the directional control valve 22 is changed over,
one of a boom-raising control signal pressure Du and a jack 45 pressure oil is delivered from the variable displacement
up control signal pressure G, the shuttle valve 305 selects the hydraulic pump 21 at a flow rate corresponding to a control
higher one of an arm-crowding control signal pressure Ec and signal pressure (a stroke of the pilot control unit 23), and the
an arm-dumping control signal pressure Ed, the shuttle valve pressure oil is fed to the bottom chamber 11a or rod chamber
306 selects the higher one of a Swing-to-right control signal
11b of the hydraulic boom cylinder 11 to cause an extension
pressure Frand a Swing-to-left control signal pressure Fl, and 50 or contraction of the hydraulic boom cylinder 11.
The hydraulic selector valve 318 is a proportional reducing
the shuttle valve 307 selects the higher one of control signal
pressures from paired pilot valves in a reserve pilot control valve which, based on the highest pressure selected at the
unit arranged when a reserve actuator is connected to a shuttle valve 315 and guided to a pressure-receiving part
reserve directional control valve.
3.18a, is operated to produce a control signal pressure (front
The shuttle valves 308-310 are arranged in a second stage 55 operation Xf) from the pressure of the pilot pump 24. When
of the shuttle valve group 30. The shuttle valve 308 selects the the highest pressure selected at the shuttle valve 315 is lower
higher one of the control signal pressures selected by the than the reservoir pressure, this hydraulic selector valve 318
shuttle valve 301 and shuttle valve 302, respectively, in the is at the position indicated in the figure to reduce the control
first stage, the shuttle valve 309 selects the higher one of the signal pressure to the reservoir pressure. When the highest
control signal pressures selected by the shuttle valve 304 and 60 pressure selected at the shuttle valve 315 becomes equal to or
shuttle valve 305, respectively, in the first stage, and the higher than the reservoir pressure, on the other hand, the
shuttle valve 310 selects the higher one of the control signal hydraulic selector valve 318 is changed over from the position
pressures selected by the shuttle valve 306 and shuttle valve indicated in the figure, and outputs the pressure of the pilot
307, respectively, in the first stage.
pump 24 after reducing it to a control signal pressure corre
The shuttle valves 311.312 are arranged in a third stage of 65 sponding to the level of the highest pressure. A Swing brake
the shuttle valve group 30. The shuttle valve 311 selects the cylinder and travel communication valve (not shown) are
higher one of the control signal pressures selected by the operated by this control signal pressure (front operation Xf).
23
the pilot pump 24, the flow control valve 26 connected on the
upstream side of the directional control valve 22 to the meter
in port of the directional control valve 22 and change-over
controlled by the jack-up selector valve 25, the center bypass
US 8,336,443 B2
25
26
Upon
performing
the
boom-raising
operation, the pressure
This sixth embodiment is basically different from the first
embodiment in the construction that the regulator (Swash oil produced at the pilot control unit 23 enters the boom
angle control means) 21a and the shuttle valve group (Swash raising signal input port Du of the shuttle valve group 30 and
angle instruction means) 30 for outputting a Swash angle is Subjected together with plural other control signals to high
control signal to the regulator 21a are arranged. A description 5 est pressure selection, and the thus-selected highest pressure
will, therefore, be made only about operations relevant to the changes over the hydraulic selector valve 317. As a result, a
construction different from the first embodiment.
pressure corresponding to the highest pressure is outputted as
When the control lever 23a is operated in the leftward a pump control signal Xp1 from the shuttle valve group 30,
direction as viewed in the figure, that is, in the boom-lowering and the variable displacement hydraulic pump 21 is increas
direction from the situation that the control lever 23a is at the 10 ingly controlled via the regulator 21a.
neutral position and no pulling force is applied on the hydrau
The hydraulic working machine according to this embodi
lic boom cylinder 11, the boom 5 is caused to turn in the ment is designed to monitor changes in the bottom pressure of
the hydraulic boom cylinder 11 and, when the bottom pres
downward direction (undergoes a so-called free fall).
During the freefall of the boom 5, the pressure oil produced sure on the hydraulic boom cylinder 11 is equal to or higher
at the pilot control unit 23 does not enterajack-up signal input 15 than the predetermined pressure upon lowering the boom, to
port G of the shuttle valve group 30 but enters a boom change over the jack-up selector valve 25 to the selected
lowering signal input port Dd. The pressure at the jack-up position 25a, and accordingly, to change over the selector
signal input port G is subjected together with other plural valve 262 in the flow control valve 26 to the selected position
control signals to highest pressure selection, and the thus 26a and the center bypass selector valve 27 to the valve
selected highest pressure changes over the hydraulic selector element position 27a such that the pressure oil delivered from
valve 317. When no other pilot control unit (not shown) is the variable displacement hydraulic pump 21 is not fed to the
operated, however, the hydraulic selector valve 317 is not rod chamber 11b of the hydraulic boom cylinder 11. It is,
changed over and is retained in the state of FIG.9. As a result, therefore, possible to reduce the horsepower consumption of
the reservoir pressure is outputted as a pump control signal the pump upon performing a simple boom-lowering opera
Xp1 from the shuttle valve group 30, and the variable dis 25 tion which does not require a pressing force for jacking up the
placement hydraulic pump 21 is decreasingly controlled via body. As the pressure oil delivered from the variable displace
the regulator 21a.
ment hydraulic pump 21 is not fed to the rod chamber 11 of
When the bottom pressure is lower than the change-over the hydraulic boom cylinder 11 upon performing a simple
pressure for the jack-up selector valve 25 in the situation that boom-lowering operation, it is possible to relatively increase
the control lever 23a has been operated in the boom-lowering 30 the pressure oil to be fed from the variable displacement
direction, on the other hand, the pressure oil fed from the hydraulic pump 21 to the hydraulic arm cylinder 12 and
variable displacement hydraulic pump 21 to the meter-in port hydraulic bucket cylinder 13 upon operating the boom 5 in
of the directional control valve 22 through the line 33 is fed combination with one or more other working elements, for
together with the regenerated oil, which has been discharged example, the arm 6 and/or bucket 7. This makes it possible to
from the bottom chamber 11a, to the rod chamber 11b of the 35 improve the energy efficiency of the hydraulic working
hydraulic boom cylinder 11 through the line 35 as in the first machine. When the bottom pressure on the hydraulic boom
embodiment, thereby making it possible to produce a strong cylinder 11 is lower than the predetermined pressure upon
pressing force Such as a jack-up force for the body.
lowering the boom, on the other hand, the jack-up selector
Upon performing a jack-up, the pressure oil produced at valve 25 is changed over to the selected position 25b, and as
the pilot control unit 23 enters the jack-up signal input portG 40 a result, the selector valve 262 in the flow control valve 26 is
of the shuttle valve group 30 and is subjected together with changed over to the selected position 26b and the center
plural other control signals to highest pressure selection, and bypass selector valve 27 is changed over to the selected posi
the thus-selected highest pressure changes over the hydraulic tion 27b such that the pressure oil delivered from the variable
selector valve 317. As a result, a pressure corresponding to the displacement hydraulic pump 21 is fed to the rod chamber
highest pressure is outputted as a pump control signal Xp1 45 11b of the hydraulic boom cylinder 11. It is, therefore, pos
from the shuttle valve group 30, and the variable displace sible to produce a large pressing force at the boom 5 and to
ment hydraulic pump 21 is increasingly controlled via the jack up the body.
regulator 21a.
The displacement of the variable displacement hydraulic
When the control lever 23a is operated in the rightward pump 21 is decreasingly controlled when the bottom pressure
direction as viewed in the figure, that is, in the boom-raising 50 on the hydraulic boom cylinder 11 is equal to or higher than
direction, on the other hand, a boom-raising pilot pressure is the predetermined pressureupon lowering the boom 5, but the
outputted to the pilot line 41 by the pressure oil fed from the displacement of the variable displacement hydraulic pump 21
pilot pump 24, so that the directional control valve 22 is is increasingly controlled by the regulator 21a when the bot
changed over to the selected position 22c. As a result, the tom pressure on the hydraulic boom cylinder 11 is lower than
pressure oil discharged from the rod chamber 11b is caused to 55 the predetermined pressure upon lowering the boom 5. It is,
return to the reservoir 28 through the line 35, directional therefore, possible to reduce the horsepower consumption of
control valve 22 and line 39. Accordingly, the bottom pres the pump upon performing a simple boom-lowering opera
Sure becomes lower than the operation pressure for the jack tion. In addition, the pressure oil can be promptly fed as much
up selector valve 25, the jack-up selector valve 25 is changed as needed to the hydraulic boom cylinder 11 upon performing
over to the selected position 25b, and the flow control valve 26 60 a pressing operation of the boom 5. It is, accordingly, possible
is changed over to the selected position 26b. Therefore, the to Smooth effect a Switchover from a simple lowering opera
pressure oil fed from the variable displacement hydraulic tion of the boom 5 to a pressing operation.
pump 21 to the meter-in port of the directional control valve
Other elements, which have not been described specifi
22 through the line 32, flow control valve 26 and line 33 is fed cally, and their operations are constructed likewise and per
to the bottom chamber 11a through the line 34, the hydraulic 65 formed similarly as in the above-described first embodiment.
It is also to be noted that, although the hydraulic circuit for
boom cylinder 11 is caused to extend, and the boom 5 is
driving the hydraulic boom cylinder 11 was described by way
caused to turn in the upward direction.
US 8,336,443 B2
27
of example in each of the above-described embodiments, the
gist of the present invention is not limited to Such hydraulic
circuits but hydraulic circuits for driving hydraulic cylinders
for other working elements can be formed into similar con
structions as described above.
For example, the hydraulic arm cylinder 12 can be men
tioned as a hydraulic cylinder for another working element.
As an operation for performing a jack-up by this hydraulic
arm cylinder 12, the arm 6 is firstly placed on a side more
28
tor valve 25 retains the valve element position 25a, so that the
selector valve 262 in the flow control valve 26 is changed over
to the selected position 26a and the center bypass selector
valve 27 retains the valve element position 27a. When the
solenoid valve 52 is changed over to the selected position 52b
to perform a boom operation, on the other hand, a pilot pres
Sure which serves as a boom-lowering signal is fed to the pilot
lines 55.56 via the solenoid valve 52. Accordingly, the jack
up selector valve 25 is changed over to the selected position
forward than a location where the arm 6 and the boom 6 are 10 25b, so that the selector valve 262 in the flow control valve 26
connected with each other, the hydraulic arm cylinder 12 is
caused to extend with the bucket 7 pressed against the ground,
is changed over to the selected position 26b and the center
bypass selector valve 27 is changed over to the selected posi
and the arm 6 is caused to turn toward the seat until the arm
tion 27b.
stands upright. To perform this operation, the pressure oil is
When the selector valve 262 has been changed over to the
guided to the side of the unillustrated bottom chamber of the 15 selected position 26a and the center bypass selector valve 27
hydraulic arm cylinder 12 such that the hydraulic arm cylin retains the valve element position 27a, the pressure oil to be
der 12 is caused to extend. A strong force can be produced fed to the rod chamber 11b consists solely of the regenerated
upon performing a jack-up by constructing Such that the oil discharged from the bottom chamber 11a and the boom 5
pressure in the rod chamber of the hydraulic arm cylinder 12 undergoes a free fall, as described in connection with the first
is monitored at this time and the pressure oil is guided to the embodiment. In this case, a pump control signal Xp1 corre
bottom chamber of the arm cylinder when the pressure in the sponding to the reservoir pressure is outputted from the
rod chamber is low.
shuttle valve group 30 to the regulator 21a, and the displace
ment of the variable displacement hydraulic pump 21 is
(Seventh Embodiment of the Hydraulic Circuit)
With reference to FIG. 10, a description will next be made decreasingly controlled. When the jack-up selector valve 25
of the seventh embodiment of the hydraulic circuit arranged 25 has been changed over to the selected position 25b and the
on the hydraulic working machine. FIG. 10 is a circuit dia center bypass selector valve 27 has been changed over to the
gram of the hydraulic circuit according to the seventh selected position 27b, on the other hand, the regenerated oil
embodiment, and as clearly seen from this figure, the hydrau and the pressure oil fed from the variable displacement
lic circuit of this embodiment is characterized in that change hydraulic pump 21 are combined and fed to the rod chamber
over controls of the jack-up selector valve and center bypass 30 11b and a strong pressing force Such as a jack-up force for the
selector valve are performed by a solenoid valve.
body can be obtained, as described in connection with the first
In FIG. 10, reference numeral 51 indicates the pressure embodiment. In this case, a pump control signal Xp1 corre
sensor for sensing a bottom pressure on the hydraulic boom sponding to the highest pressure selected at the shuttle valve
cylinder 11, reference numeral 52 the solenoid valve for group 30 is outputted to the regulator 21a from the shuttle
changing over the jack-up selector valve 25 and center bypass 35 valve group 30, and the displacement of the variable displace
ment hydraulic pump 21 is increasingly controlled.
selector valve 27, reference numeral 53 the controller for
receiving an output signal from the pressure sensor 51 and
The hydraulic working machine according to this embodi
outputting an instruction current value to be fed to the signal ment can bring about similar advantageous effects as the
input part of the solenoid valve 52, reference numeral 54 the hydraulic working machine according to the sixth embodi
line branching out from the pilot line 40 and communicating 40 ment. In addition, it can omitat least the line which connects
to the solenoid valve 52, reference numeral 55 the pilot line the bottom chamber 11a of the hydraulic boom cylinder 11
connecting the signal port of the jack-up selector valve 25 and and the signal port of the jack-up selector valve 25 with each
other, thereby making it possible to achieve simplification of
the solenoid valve 52 with each other, and reference numeral
56 the pilot line connecting the signal port of the center the hydraulic circuit.
bypass selector valve 27 and the solenoid valve 52 with each 45 (Eighth Embodiment of the Hydraulic Circuit)
With reference to FIG. 11, a description will next be made
other. Other elements which are the same or equivalent to
corresponding elements in FIG. 8 are shown by the same of the eighth embodiment of the hydraulic circuit arranged on
reference numerals.
the hydraulic working machine. FIG. 11 is a circuit diagram
Stored in the controller 53 is the relationship between the of the hydraulic circuit according to the eighth embodiment,
values of bottom pressures on the hydraulic boom cylinder 11 50 and as clearly seen from this figure, the hydraulic circuit of
as detected by the pressure sensor 51 and the instruction this embodiment is characterized in that two solenoid valves
current values to be fed to the signal input part of the solenoid are arranged as a jack-up selector valve, and change-over
valve 52. When a bottom pressure value detected by the controls of these two solenoid valves are performed based on
pressure sensor 51 is within the range of bottom pressure the bottom pressure on the hydraulic boom cylinder and the
values upon free falling of the boom, namely, is equal to or 55 pilot pressure to the directional control valve.
higher than the predetermined pressure P0, the solenoid valve
In FIG. 11, reference numeral 51 indicates the first pressure
52 retains the valve element position 52a. When a bottom sensor for sensing a bottom pressure on the hydraulic boom
pressure value detected by the pressure sensor 51 is within the cylinder 11, reference numerals 61.62 the first and second
range of bottom pressures in the situations that pressing Solenoid valves which make up the jack-up selector valve,
forces are applied to the boom 5, namely, is lower than the 60 reference numeral 63 the second pressure sensor for sensing
predetermined pressure P0, on the other hand, an instruction a pilot pressure in the pilot line 40, reference numeral 64 the
current is outputted to change over the solenoid valve 52 to controller for receiving an output signal from the first pres
Sure sensor 51 and an output signal from the second pressure
the selected position 52b.
When the solenoid valve 52 retains the valve element posi sensor 63 and outputting instruction current values to change
tion 52a, a pilot pressure which serves as a boom-lowering 65 over the selected positions of the first and second solenoid
signal is cut off at the solenoid valve 52 and no pilot pressure valves 61,62, reference numeral 65 the pilot line connecting
arises in the pilot lines 55.56. Accordingly, the jack-up selec the first solenoid valve 61 and the signal port of the selector
US 8,336,443 B2
29
valve 262 in the flow control valve 26 with each other, and
reference numeral 66 the pilot line connecting the second
solenoid valve 62 and the signal port of the center bypass
selector valve 27 with each other. Other elements which are
30
shuttle valve group 30 to the regulator 21a, and the displace
ment of the variable displacement hydraulic pump 21 is
decreasingly controlled. When the valve element positions of
the first solenoid valve 61 and second solenoid valve 62,
the same or equivalent to corresponding elements in FIG. 8 5 which make up the jack-up selector valve 25, have been
are shown by the same reference numerals.
changed over to the selected positions 61b,62b, respectively,
The controller 64 is constructed, as depicted in FIG. 11, of and the center bypass selector valve 27 has been changed over
the first storage unit 71 in which the relationship between the to the selected position 27b, on the other hand, the regener
values of bottom pressures on the hydraulic boom cylinder 11 ated oil and the pressure oil fed from the variable displace
as sensed by the first pressure sensor 51 and the instruction 10 ment hydraulic pump 21 are combined and fed to the rod
current values to be fed to the signal input parts of the first and chamber 11b and a strong pressing force Such as a jack-up
second Solenoid valves 61.62 is stored, the second storage
unit 72 in which the relationship between pilot pressures force for the body is produced, as described in connection
(boom-lowering signals) in the pilot line 40 as sensed by the with the first embodiment. In this case, a pump control signal
second pressure sensor 63 and the instruction current values 15 Xp1 corresponding to the highest pressure selected at the
to be fed to the signal input part of the first solenoid valve 62 shuttle valve group 30 is outputted from the shuttle valve
is stored, and the lowest selection circuit 73 for selecting the group 30 to the regulator 21a, and the displacement of the
lower one of an instruction current value outputted from the variable displacement hydraulic pump 21 is increasingly con
first storage unit 71 and an instruction current value outputted trolled.
The hydraulic working machine according to this embodi
from the second storage unit 72 and feeding it to the signal
ment can also bring about similar advantageous effects as the
input part of the first solenoid value 62.
According to the controller 64 in this embodiment, when hydraulic working machine according to the seventh embodi
the value of a bottom pressure on the hydraulic boom cylinder ment.
11 as sensed by the pressure sensor 51 is within the range of (Ninth Embodiment of the Hydraulic Circuit)
bottom pressure values upon freefalling of the boom, namely, 25 With reference to FIG. 12, a description will next be made
is equal to or higher than the predetermined pressure P0, an of the fourth embodiment of the hydraulic circuit arranged on
instruction current value outputted from the first storage unit the hydraulic working machine. FIG. 12 is a circuit diagram
71 is a small value so that the first solenoid valve 61 retains the
of the hydraulic circuit according to the ninth embodiment,
valve element position 61a, and irrespective of the level of an and as clearly seen from this figure, the hydraulic circuit of
instruction current outputted from the second storage unit 72, 30 this embodiment is characterized in that change-over controls
the instruction current of the small value is outputted from the of the directional control valve 22, flow control valve 26 and
center bypass selector valve 27 are performed by a pilot
lowest selection circuit 73. Therefore, the second solenoid
valve 62 also retains the valve element position 62a. As the pressure reduced in pressure by the reducing valve 23b con
pressure oil delivered from the pilot pump 24 is hence fed to stituting the pilot control unit 23, namely, a boom-lowering
the signal port of the selector valve 262 in the flow control 35 signal.
In FIG. 12, reference numeral 51 indicates the first pressure
valve 26 via the first solenoid valve 61 and the pilot line 65,
the selector valve 262 is changed over to the selected position sensor for sensing a bottom pressure on the hydraulic boom
26a. Further, the pressure oil delivered from the pilot pump 24 cylinder 11, reference numerals 81.82 the first and second
is cut off at the second solenoid valve 62, so that no pilot Solenoid valves which make up the jack-up selector valve,
pressure arises in the pilot line 66 and the center bypass 40 reference numeral 83 the controller for receiving an output
signal from the first pressure sensor 51 and outputting instruc
selector valve 27 retains the valve element position 27a.
When the value of a bottom pressure on the hydraulic boom tion current values to change over the selected positions of the
cylinder 11 as sensed by the pressure sensor 51 is within the first and second solenoid valves 81,82, reference numeral 84
range of bottom pressure values in situations that pressing the pilot line branching out from the pilot line 40 and con
forces are applied to the boom 5, namely, is lower than the 45 necting it to the first solenoid valve 81, reference numeral 85
predetermined pressure P0, an instruction current value out the pilot line branching out from the pilot line 40 and con
putted from the first storage unit 71 is a large value so that the necting it to the second solenoid valve 82, reference numeral
first solenoid valve 61 is changed over to the selected position 86 the pilot line connecting the first solenoid valve 81 and the
61b. From the lowest selection circuit 73, a current corre
signal port of the selector valve 262 in the flow control valve
sponding to an instruction current outputted from the second 50 26 with each other, reference numeral 87 the pilot line con
storage unit 72 is also outputted. When a boom-lowering necting the second Solenoid valve 82 and the signal port of the
operation is performed, the second solenoid valve 62 and the center bypass selector valve 27 with each other, reference
center bypass selector valve 27 are, therefore, changed overto numeral 88 the pilot line connecting the second solenoid
the selected position 62b and the selected position 27b, valve 82 and the boom-raising, reducing valve 23c arranged
respectively. When no boom-lowering operation is per 55 in the pilot control unit 23 with each other, and numeral 89 the
check valve arranged at the point of connection between the
formed, on the other hand, the second solenoid valve 62
retains the valve element position 62a so that the center pilot line 87 and the pilot line 88. Other elements which are
bypass selector valve 27 retains the valve element position the same or equivalent to corresponding elements in FIG. 8
27a.
are shown by the same reference numerals.
When the selector valve 262 in the flow control valve 26 60
The controller 83 is constructed, as depicted in FIG. 12, of
has been changed over to the selected position 26a and the the first storage unit 91 in which the relationship between the
center bypass selector valve 27 retains the valve element values of bottom pressures on the hydraulic boom cylinder 11
position 27a, only the regenerated oil discharged from the as sensed by the first pressure sensor 51 and the instruction
bottom chamber 11a is fed to the rod chamber 11b and the
current value to be fed to the signal input part of the first
boom 5 undergoes a free fall, as described in connection with 65 solenoid valve 81 is stored, and the second storage unit 92 in
the first embodiment. In this case, a pump control signal Xp1 which the relationship between the values of bottom pres
corresponding to the reservoir pressure is outputted from the sures on the hydraulic boom cylinder 11 as sensed by the first
US 8,336,443 B2
31
pressure sensor 51 and the instruction current value to be fed
to the signal input part of the second solenoid valve 82 is
stored.
32
The hydraulic working machine according to this embodi
ment can also bring about similar advantageous effects as the
hydraulic working machine according to the seventh embodi
According to the controller 83 in this embodiment, when ment.
the value of a bottom pressure on the hydraulic boom cylinder 5 (Tenth Embodiment of the Hydraulic Circuit)
11 as sensed by the pressure sensor 51 is within the range of
With reference to FIG. 13 and FIG. 14, a description will
bottom pressure values upon freefalling of the boom, namely, next be made of the tenth embodiment of the hydraulic circuit
is equal to or higher than the predetermined pressure P0, the arranged on the hydraulic working machine. FIG. 13 is a
first solenoid value 81 retains the valve element position 81a circuit diagram of the hydraulic circuit according to the tenth
by an instruction current value outputted from the first storage 10 embodiment, and FIG. 14 is a construction diagram of a
unit 91 and the second solenoid valve 82 retains the valve
shuttle valve group arranged in the hydraulic circuit of the
element position 82a by an instruction current value output tenth embodiment. As clearly seen from these figures, the
ted from the second storage unit 92. When a boom-lowering hydraulic circuit of this embodiment is characterized in that a
operation is performed, a boom-lowering pilot pressure is fed track-unit-driving, hydraulic circuit is combined with a
from the pilot line 40 to the signal port of the selector valve 15 boom-driving, hydraulic circuit.
262 in the flow control valve 26 through the pilot line 84, first
In FIG. 13, reference numeral 8 indicates the right-track
solenoid valve 81 and pilot line 86, so that the selector valve hydraulic motor, reference numeral 9 the left-track hydraulic
262 is changed over to the selected position 26a and the pilot motor, reference numeral 101 the second variable displace
line 85 is cut off at the second solenoid valve 82. As a conse
ment hydraulic pump, reference numeral 101a a second regu
quence, no pilot pressure arises in the pilot line 87 and the lator (Swash angle control means) for controlling the dis
center bypass selector valve 27 retains the valve element placement of the second variable displacement hydraulic
position 27a.
pump 101, reference numeral 102 the second directional con
When the value of a bottom pressure on the hydraulic boom trol valve for controlling a flow of pressure oil to be fed from
cylinder 11 as sensed by the pressure sensor 51 is within the the variable displacement hydraulic pump 21 to the right
range of bottom pressure values in situations that pressing 25 track hydraulic motor 8, reference numeral 103 a third direc
forces are applied to the boom 5, namely, is lower than the tional control valve for controlling a flow of pressure oil to be
predetermined pressure P0, the first solenoid valve 81 is fed from the second variable displacement hydraulic pump
changed over to the selected position 81b by an instruction 101 to the left-track hydraulic motor 9, reference numeral 104
current value outputted from the first storage unit 91 and the the fourth directional control valve for controlling a flow of
second solenoid valve 82 is changed over to the selected 30 pressure oil to be fed from the second variable displacement
position 82b by an instruction current value outputted from hydraulic pump 101 to the hydraulic boom cylinder 11, ref
the second storage unit 92. The pilot line 84 is, therefore, cut erence numeral 105the selector valve for feeding the pressure
off at the first solenoid valve 81. Accordingly, no pilot pres oil, which is fed from the first variable displacement hydrau
sure arises in the pilot line 86, the flow control valve 26 is lic pump 21, to the side of the left-track hydraulic motor 9
changed over to the selected position 26b, and the pilot line 40 35 upon performing a boom-lowering operation, reference
and the pilot line 87 are brought into a state communicated numeral 106 the shuttle valve for applying a change-over
with each other. When a boom-lowering operation is per signal to the selector valve 105 when a boom operation has
formed, a boom-lowering pilot pressure is, therefore, fed to been performed, reference numeral 107 the line connecting
the signal port of the center bypass selector valve 27 through the second variable displacement hydraulic pump 101 and the
the pilot line 40, pilot line 85, second solenoid valve 82 and 40 fourth directional control valve 104 with each other, reference
the pilot line 87. As a consequence, the center bypass selector numeral 108 the center bypass passage communicating the
second variable displacement hydraulic pump 101 and the
valve 27 is changed over to the selected position 27b.
When the selector valve 262 in the flow control valve 26
reservoir 28 with each other, reference numeral 109 the line
has been changed over to the selected position 26a and the connecting the fourth directional control valve 104 and the
center bypass selector valve 27 has been changed over to the 45 rod chamber 11b of the hydraulic boom cylinder 11 with each
selected position 27a, only the regenerated oil discharged other, reference numeral 110 the line connecting the fourth
from the bottom chamber 11a is fed to the rod chamber 11b
directional control valve 104 and the bottom chamber 11a of
and the boom 5 undergoes a free fall, as described in connec the hydraulic boom cylinder 11 with each other, reference
tion with the first embodiment. In this case, a pump control numeral 111 the check valve arranged on the line 110, refer
signal Xp1 corresponding to the reservoir pressure is output 50 ence numeral 112 a line connecting the variable displacement
ted from the shuttle valve group 30 to the regulator 21a, and hydraulic pump 21 and the selector valve 105 with each other,
the displacement of the variable displacement hydraulic reference numeral 113 the check valve arranged on the line
pump 21 is decreasingly controlled. When the first solenoid 112, reference numeral 114 the line connecting the selector
valve 81 and second solenoid valve 82, which make up the valve 105 and the third directional control valve 103 with
jack-up selector valve 25, have been changed over to the 55 each other, reference numeral 115 the pilot line guiding a pilot
selected positions 81b,82b, respectively, and the center pressure, which serves as a boom-lowering signal, to the
bypass selector valve 27 has been changed over to the selected jack-up selector valve 25, reference numeral 116the pilot line
position 27b, on the other hand, the regenerated oil and the for feeding a boom-lowering signal to the signal port of the
pressure oil fed from the variable displacement hydraulic fourth directional control valve 104, reference numeral 117
pump 21 are combined and fed to the rod chamber 11b and a 60 the pilot line for feeding a boom-raising signal to the signal
strong pressing force Such as a jack-up force for the body is port of the fourth directional control valve 104, and reference
produced, as described in connection with the first embodi numeral 118 the pilot line for feeding a change-over signal to
ment. In this case, a pump control signal Xp1 corresponding the signal port of the selector valve 105. Other elements
to the highest pressure selected at the shuttle valve group 30 which are the same or equivalent to corresponding elements
is outputted from the shuttle valve group 30 to the regulator 65 in FIG. 8 are shown by the same reference numerals.
21a, and the displacement of the variable displacement
It is to be noted that as shown in FIG. 14, the shuttle valve
hydraulic pump 21 is increasingly controlled.
group 30 arranged in the hydraulic circuit in this embodiment
US 8,336,443 B2
33
34
has a construction with a shuttle valve 316 and a hydraulic position 26a and the center bypass selector valve 27 is also
selector valve 319 added to the shuttle valve group in FIG.9. maintained at the valve element position 27a. Accordingly,
The shuttle valve 316 is arranged in a sixth stage of the shuttle the pressure oil delivered from the variable displacement
valve group 30, and selects the higher one of the control signal hydraulic pump 21 is guided to the reservoir 28 through the
pressures selected by the shuttle valve 302 in the first stage line 31, the center bypass port of the directional control valve
and the shuttle valve 312 in the third stage, respectively. The 22, the line37, the center bypass selector valve 27 and the line
hydraulic selector valve 319 is a proportional reducing valve 38, and the pressure oil delivered from the second variable
which, based on the highest pressure selected at the shuttle displacement hydraulic pump 101 is guided to the reservoir
valve 316 and guided to a pressure-receiving part 319a, is 28 through the line 107, the line 108 and the center bypass
operated to produce a control signal pressure (pump control 10 port of the third directional control valve 103. As a conse
signal Xp2) from the pressure of the pilot pump 24. When the
the pressure oil is fed neither to the bottom chamber
highest pressure selected at the shuttle valve 316 is lower than quence,
nor the rod chamber 11b of the hydraulic boom cylinder
the reservoir pressure, this hydraulic selector valve 319 is at 11a
11. Therefore, only the regenerated oil discharged from the
the position indicated in the figure to reduce the control signal
pressure to the reservoir pressure. When the highest pressure 15 bottom chamber 11a is fed to the rod chamber 11b, the
selected at the shuttle valve 316 becomes equal to or higher hydraulic boom cylinder 11 contracts under the dead weight
than the reservoir pressure, on the other hand, the hydraulic of the boom 5, and the boom 5 undergoes a free fall.
During the freefall of the boom.5, the pressure oil produced
selector valve 319 is changed over from the position indicated
in the figure, and outputs the pressure of the pilot pump 24 at the pilot control unit 23 does not enter the jack-up signal
after reducing it to a control signal pressure corresponding to input port G of the shuttle valve group 30 but enters the
the level of the highest pressure. The regulator 101 a for the boom-lowering signal input port Dd. The pressure at the
second variable displacement hydraulic pump 101 is operated jack-up signal input port G is subjected together with other
by the control signal pressure (pump control signal Xp2).
plural control signals to highest pressure selection, and the
A description will hereinafter be made about operations of thus-selected highest pressure changes over the hydraulic
the hydraulic working machine according to the tenth 25 selector valve 317. When no other pilot control unit (not
embodiment constructed as described above.
shown) is operated, however, the hydraulic selector valve 317
When the control lever 23a is at the neutral position, the is not changed over and is retained in the state of FIG. 4. As a
directional control valve 22 and the fourth directional control
result, the reservoir pressure is outputted as pump control
valve 104 retain the neutral position 22b and the neutral signals Xp1.Xp2 from the shuttle valve group 30, and the
position 104b, respectively, as illustrated in FIG. 13. Accord 30 variable displacement hydraulic pumps 21.101 are decreas
ingly, the jack-up selector valve 25 is changed over to the ingly controlled via the regulators 21a, 101a.
selected position 25a by the bottom-side pressure of the
When the bottom pressure becomes lower than the operat
hydraulic boom cylinder 11. In this state, the pilot line 43 is in ing pressure for the jack-up selector valve 25 in the situation
communication with the reservoir 28, so that the center
that the control lever 23a has been operated in the boom
bypass selector valve 27 retains the valve element position 35 lowering direction, on the other hand, the jack-up selector
27a and the selector valve 105 retains the valve element
valve 25 is changed over to the selected position 25b, so that
position 105a. Accordingly, the pressure oil delivered from the pilot line 45 is brought into communication with the
the variable displacement hydraulic pump 21 is guided to the reservoir 28 via the jack-up selector valve 25 and the selector
reservoir 28 through the line 31, the center bypassport of the valve 262 in the flow control valve 26 is changed over to the
directional control valve 22, the line 37, the center bypass 40 valve element position 26b. The pressure oil delivered from
selector valve 27 and the line 38. Further, the pressure oil the variable displacement hydraulic pump 21 is, therefore, fed
delivered from the second variable displacement hydraulic to the meter-in port of the directional control valve 22 through
pump 101 is guided to the reservoir 28 through the line 107. the line 32, the flow control valve 26 and the line 33. Respon
the line 108 and the center bypassport of the third directional sive to a change-over of the jack-up selector valve 25, the pilot
control valve 103. No pressure oil is, therefore, fed to the 45 pressure is fed as a boom-lowering signal to the signal port of
bottom chamber 11a and rod chamber 11b of the hydraulic the center bypass selector valve 27 through the pilot line 115,
jack-up selector valve 25 and pilot line 43. As a consequence,
bottom cylinder 11.
When the control lever 23a is operated in the leftward the center bypass selector valve 27 is changed over to the
direction as viewed in the figure, that is, in the boom-lowering selected position 27b, the center bypass selector valve 27 is
direction in the above-described state, the pilot pressure 50 changed over to the selected position 27b, and the boom
which has been fed from the pilot pump 24 and reduced in lowering signal is also fed to the signal port on the boom
pressure by the reducing valve 23b is outputted to the pilot lowering side of the fourth directional control valve 104
line 40, and the directional control valve 22 is changed over to through the pilot line 116. The fourth directional control valve
the selected position 22a. Further, this pilot pressure is guided 104 is, therefore, changed over to the selected position 104a.
to the pilot line 115 and then to the signal port of the selector 55 Accordingly, the pressure oil delivered from the variable dis
valve 262 in the selector valve 262 via the jack-up selector placement hydraulic pump 21 is fed to the rod chamber 11b of
valve 25, so that the selector valve 262 is changed over to the the hydraulic boom cylinder 11, the pressure oil delivered
selected position 26a. As a consequence, a portion of the from the second variable displacement hydraulic pump 101 is
return oil from the bottom chamber 11a is regenerated in the fed to the rod chamber 11b of the hydraulic boom cylinder 11
rod chamber 11b via the restrictor 29b, check valve 29c and 60 through the fourth directional control valve 104, line 109 and
line 35, and the regenerated oil discharged from the bottom
line35, and the rest of the return oil is returned to the reservoir
28 via the restrictor 29a and line 39.
chamber 11a, the pressure oil fed from the variable displace
When the bottom pressure is higher than the operating ment hydraulic pump 21 and the pressure oil fed from the
pressure for the jack-up selector valve 25 in the above-de second variable displacement hydraulic pump 101 are com
scribed situation, the jack-up selector valve 25 is maintained 65 bined and fed to the rod chamber 11b. It is hence possible to
at the valve element position 25a, so that the selected position produce a strong pressing force like a jack-up force for the
of the flow control valve 26 is also maintained at the selected
body.
US 8,336,443 B2
35
Upon performing a jack-up, the pressure oil produced at
the pilot control unit 23 enters the jack-up signal input portG
of the shuttle valve group 30 and is subjected together with
plural other control signals to highest pressure selection, and
the thus-selected highest pressure changes over the hydraulic
selector valve 317. As a result, a pressure corresponding to the
highest pressure is outputted as pump control signals Xp1.
Xp2 from the shuttle valve group 30, and the variable dis
placement hydraulic pumps 21.101 are increasingly con
10
trolled via the regulators 21a, 101a.
Further, the boom-operating pilot pressure is guided to the
Selector valve 105 via the shuttle valve 106 and line 118.
36
pump is not fed to a non-holding pressure feeding side of
said hydraulic cylinder, and
when the holding pressure on said hydraulic cylinder is
lower than the predetermined pressure upon lowering
said working element, said jack-up selector valve is
changed over to a second selected position to change
over said flow-line changing means to the open side Such
that pressure oil delivered from said main pump is fed to
a non-holding pressure side of said hydraulic cylinder
via said directional control valve.
2. A hydraulic working machine according to claim 1,
wherein as said jack-up selector valve, said hydraulic work
ing machine is provided with a hydraulically-piloted selector
Accordingly, the selector valve 105 is changed over to the
selected position 105b, so that the pressure oil delivered from valve.
the variable displacement hydraulic pump 21 is fed to the 15 3. A hydraulic working machine provided with a first and
left-track and right-track hydraulic motors 8.9 via the second second main pumps, a first track unit for being driven by
directional control valve 102 and third directional control
pressure oil delivered from said first main pump, a second
valve 103, respectively. As a consequence, when the boom track unit for being driven by pressure oil delivered from said
and the tracks are operated at the same time, the pressure oil second main pump, a first directional control valve for con
from the variable displacement hydraulic pump 21 is fed to trolling a flow of pressure oil to be fed from said first main
the left-track and right-track motors 8.9 and the pressure oil pump to said first track unit, a second directional control valve
from the second variable displacement hydraulic pump 101 is for controlling a flow of pressure oil to be fed from said
fed to the hydraulic boom cylinder 11, thereby making it second main pump to said second track unit, a working ele
possible to jackup the body by the combined operation of the ment, a double-acting hydraulic cylinder arranged for exten
25 sion or contraction by pressure oil, which is delivered from
track operation and the boom-lowering operation.
It is to be noted that, although a hydraulically-piloted selec said first and second main pumps, to drive said working
tor valve was used as the jack-up selector valve 25 in the element, a third directional control valve for controlling flows
above-described tenth embodiment, an electrohydraulic or of pressure oil to be fed from said first main pump to a bottom
Solenoid-operated selector valve can also be used as in the chamber and rod chamber of said hydraulic cylinder, a fourth
hydraulic working machines according to the seventh to ninth 30 directional control valve for controlling flows of pressure oil
embodiments.
to be fed from said second main pump to said bottom chamber
It is also to be noted that, although the hydraulic circuit for and rod chamber of said hydraulic cylinder, a first control unit
driving the hydraulic boom cylinder 11 was described by way for performing change-over controls of said first and second
of example in each of the above-described embodiments, the directional control valves, and a second control unit for per
gist of the present invention is not limited to Such hydraulic 35 forming change-over controls of said third and fourth direc
circuits but hydraulic circuits for driving hydraulic cylinders tional control valves, characterized in that said hydraulic
for other working elements can be formed into similar con working machine is provided with:
structions as described above.
a jack-up selector valve for being changed over when a
bottom pressure on said hydraulic cylinder has reached a
The invention claimed is:
40
predetermined pressure, and
1. A hydraulic working machine provided with:
a flow-line changing means for changing a flow-line for
a double-acting hydraulic cylinder arranged for extension
pressure oil, which is to be fed from said first main pump
or contraction by pressure oil, which is delivered from a
to a meter-in port of said third directional control valve,
main pump, to drive a working element,
from an open side to a closed side in response to a
change-over control of said jack-up selector valve,
a directional control valve for controlling a flow of pressure 45
wherein, when the bottom pressure on said hydraulic cyl
oil to be fed from said main pump to said hydraulic
cylinder, and
inder is equal to or higher than the predetermined pres
Sure upon lowering said working element, said jack-up
a control unit for performing a change-over control of said
Selector valve is changed over to a first selected position
directional control valve, characterized in that said
50
hydraulic working machine is provided with:
to change over said flow-line changing means to the
ajack-up selector valve for being changed over in flow-line
closed side such that pressure oil delivered from said
when a feed pressure to said hydraulic cylinder has
first and second main pumps is not fed to said rod cham
reached a predetermined pressure, and
ber of said hydraulic cylinder, and
a pilot-controlled flow-line changing means for changing a
when the bottom pressure on said hydraulic cylinder is
lower than the predetermined pressure upon lowering
flow-line for pressure oil, which is to be fed from said 55
said working element, said jack-up selector valve is
main pump to a meter-in port of said directional control
changed over to a second selected position to change
valve, from an open side to a closed side in response to
a change-over control of said jack-up selector valve
over said flow-line changing means to the open side Such
which generates a pilot hydraulic control signal from
that pressure oil delivered from said first and second
said jack-up selector valve to said pilot-controlled flow 60
main pumps is fed to said rod chamber of said hydraulic
line changing means,
cylinder via said third and fourth directional control
valves.
wherein, when a holding pressure on said hydraulic cylin
der is equal to or higher than the predetermined pressure
4. A hydraulic working machine provided with a first and
upon lowering said working element, said jack-up selec second variable displacement hydraulic pumps as main
tor valve is changed over to a first selected position to 65 pumps, a first and second Swash angle control means for
change over said flow-line changing means to the closed independently controlling displacements of said first and sec
side such that pressure oil delivered from said main ond variable displacement hydraulic pumps, respectively, a
US 8,336,443 B2
37
first track unit for being driven by pressure oil delivered from
said first variable displacement hydraulic pump, a second
track unit for being driven by pressure oil delivered from said
second variable displacement hydraulic pump, a first direc
tional control valve for controlling a flow of pressure oil to be
fed from said first variable displacement hydraulic pump to
said first track unit, a second directional control valve for
controlling a flow of pressure oil to be fed from said second
variable displacement hydraulic pump to said second track
unit, at least one working element, at least one actuator 10
arranged for extension or contraction by pressure oil, which is
delivered from said first and second variable displacement
hydraulic pumps, to drive said working element, a third direc
tional control valve for controlling a flow of pressure oil to be 15
fed from said first variable displacement hydraulic pump to
said actuator, a fourth directional control valve for controlling
a flow of pressure oil to be fed from said second variable
displacement hydraulic pump to said actuator, a pilot control
unit for performing change-over controls of said first and
second directional control valves, and a Swash angle instruc
tion means for outputting a Swash angle control signal to said
Swash angle control means in response to a signal from said
pilot control unit, characterized in that said hydraulic working
25
machine is provided with:
a jack-up selector valve for being changed over when a
holding pressure on said actuator has reached a prede
termined pressure, and
38
a flow-line changing means for changing a flow-line for
pressure oil, which is to be fed from said first variable
displacement hydraulic pump to a meter-in port of said
third directional control valve, from an open side to a
closed side in response to a change-over control of said
jack-up selector valve,
wherein, when the holding pressure on said actuator is
equal to or higher than the predetermined pressure upon
lowering said working element, said jack-up selector
valve is changed over to a first selected position to
change over said flow-line changing means to the closed
side such that pressure oil to be fed from said first and
second variable displacement hydraulic pumps to said
actuator is cut off and the displacements of said first and
second variable displacement hydraulic pumps are
decreasingly controlled, and
when the holding pressure on said actuator is lower than the
predetermined pressure upon lowering said working ele
ment, said jack-up selector valve is changed over to a
second selected position to change over said flow-line
changing means to the open side Such that pressure oil
delivered from said first and second variable displace
ment hydraulic pumps is fed to said actuator via said
third and fourth directional control valves and the dis
placements of said first and second variable displace
ment hydraulic pumps are increasingly controlled by
said Swash angle instruction means.
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